1. ECOLOGY, BEHAVIOR AND BIONOMICS
Eucalyptus Edge Effect on Quercus-Herbivore Interactions
in a Neotropical Temperate Forest
C HERNÁNDEZ-SANTIN1, M CUAUTLE1 , M DE LAS N
BARRANCO-LEÓN2, J GARCÍA-GUZMÁN1, El BADANO2,
F LUNA-CASTELLANOS1
1Depto de Ciencias Químico Biológicas, Univ de las Américas
Puebla, Cholula, Puebla, Mexico
2División de Ciencias Ambientales, Instituto Potosino de
Investigación Científica y Tecnológica, San Luis Potosí, Mexico
AbstractKeywords
Quercus , herbivory, edge effect,
Lepidoptera caterpillars
Correspondence
M Cuautle, Depto de Ciencias Químico
Biológicas, Univ de las Américas Puebla,
Cholula, Puebla, Mexico; [email protected]
hotmail.com
Edited by Martin F Pareja – UNICAMP
Received 18 June 2018 and accepted 26
April 2019
* Sociedade Entomológica do Brasil 2019

2. Fragmentation leads to the formation of edges between habitats,
which in
turn changes biotic and abiotic factors that might influence
herbivory or
plant-herbivory interactions. The aims of this study were to
describe the
herbivory community associated with oak (Quercus) and to
determine the
effects of proximity to a Eucalyptus edge and season on insect
herbivory.
We selected three forest sites that were subsequently divided
into three
quadrants located at different distances from the Eucalyptus
edge: edge
(0 m), intermediate (30 m), and oak forest interior (60 m). We
randomly
selected 10 oak trees per quadrant and conducted monthly
surveys, during
the dry and rainy season (from February to October 2010),
where we
quantified leaf area and the percentage of herbivory. These were
analyzed
using linear mixed models, with distance and season as fixed
factors and
individual and site as random factors. The primary oak
herbivores were
Lepidoptera caterpillars. We found that herbivory increased
away from
the edge but just during the rainy season, although higher
herbivory levels
were found during the dry season. These results seem to be
related to a
specialist community of herbivorous associated to the Quercus.
This study
emphasizes the importance of considering border effect,
especially within

3. Natural Protected Areas to establish strategies to improve and
maintain
native oak forest and the biodiversity of its Lepidoptera
herbivorous
community.
Introduction
Landscape modification due to anthropogenic activities (e.g.,
land conversion to agricultural or livestock) has resulted in
habitat fragmentation, one of the major threats for forest
conservation (Buckley 2000, Franklin et al 2002).
Fragmentation is defined as the disruption or breakdown of
large vegetation patches into smaller ones resulting in a dis -
continuity of resource distribution that affects species occu-
pancy, reproduction, and/or survival (Franklin et al 2002).
One of the important features of this phenomenon is an
increase in edge length relative to the forest area, particular -
ly in small habitat fragments (Laurance 1991, Laurance &
Yensen 1991, Murcia 1995, Laurance et al 2007, De
Carvalho Guimarães et al 2014). Edges are defined as bound-
aries between distinct patches types, so edge identification
depends on how patches are defined (Ries et al 2004, Wirth
et al 2008). Both physical (light, humidity, solar incidence;
Buckley 2000, Murcia 1995, Williams-Linera et al 1998) and
biotic conditions (e.g., plant-insect interactions, species and
resource distribution) are strongly altered in forest edges
relative to interior (Lidicker 1999, Bogaert et al 2001, López
2004, De Carvalho Guimarães et al 2014), and these changes
are referred to as edge effects (Wirth et al 2008). The chang-
es in the physical environment are followed by changes in
forests structure and species composition and abundance
Neotrop Entomol
https://doi.org/10.1007/s13744-019-00694-5

4. http://orcid.org/0000-0002-9694-7578
http://crossmark.crossref.org/dialog/?doi=10.1007/s13744-019-
00694-5&domain=pdf
along the forest edges (Ries et al 2004, De Carvalho
Guimarães et al 2014). Finally, changes in species composi -
tion may result in modified species interactions (De Carvalho
Guimarães et al 2014).
The ecological consequences of edge effects have been
mostly studied in terms of effects on biodiversity and species
abundance and distribution (Lidicker 1999, Bogaert et al
2001, López 2004, Medinaceli et al 2004, Connor 2006),
whereas studies on edge effects on species interactions such
as herbivory have received relatively less attention (but see,
Baraza et al 2004, Bossart and Opuni-Frimpong 2009, Liang
& Stehlik 2009, Rossetti et al 2014, De Carvalho Guimarães
et al 2014). Herbivory, defined as the consumption of plant
tissue by animals (Strauss & Zangerl 2002), is the most wide-
spread plant-insect interaction and represents an important
determinant of vegetation structure (Medinaceli et al 2004).
There are two types of herbivory: external herbivory occurs
when herbivores feed on leaves, flowers, and seeds, whereas
internal herbivory takes place under the plant’s surface and
is caused mainly by insects that cause galls or mines (Strauss
& Zangerl 2002). A meta-analysis (31 studies) of the effects of
fragmentation on herbivory, performed by De Carvalho
Guimarães et al 2014, found a significant increase in insect
richness (65%), insect abundance (14%), and plant herbivo-
rous rates (74%) on edges, compared with vegetation inte-
riors. They also found that herbivorous rates were higher
when herbivorous were chewers of the Orthoptera and
Lepidoptera orders. AccordingtoDe CarvalhoGuimarães et al
2014, edges can be considered postdisturbance recovering

5. sites, in which plant species number and/or densities incre-
ment, representing extra resources for generalist herbivo-
rous. This study is in accordance with the revision (55 studies)
made by Wirth et al (2008), who found that 82% of the
studies reported that edge promotes a positive effect on
herbivorous response (abundance, species richness).
In the study area, the native vegetation is oaks forest and
the main herbivores are Lepidoptera caterpillars. Oaks
(Quercus spp.), from the Fagaceae family, are a group of
trees and shrubs distributed throughout the Northern hemi-
sphere including Europe, Asia, and North America (Vázquez
et al 2004). In Mexico, oak-dominated forests cover 5.5% of
the country’s land total surface and include 161 Oak species
of which 109 are endemic (Arizaga et al 2009). Based on this,
Mexico is considered a center of diversification of oaks in the
American continent (Vázquez et al 2004). In the Neotropics,
oaks are widely distributed, ranging from the north of the
Mexican Transition Zone down to the south of the Colombian
Andes, and it includes the greatest oak species diversity re-
gion in the mountains of southern Mexico (Rodríguez-Correa
et al 2015). The main insect herbivores on oak species belong
to Lepidoptera and Hymenoptera which feed on leaf tissue
during the larval stage (Summerville et al 2003), and
Lepidoptera in particular represents a dominant group of
herbivores on oak by causing up to 88% of the external
herbivory on these tree species (Hochwender et al 2003,
Williams-Linera & Herrera 2003). Previous work with oak
herbivory has found that it is influenced by abiotic factors
such as light availability (Baraza et al 2004, Liang & Stehlik
2009), as well as biotic factors such as the age and size of the
plant (Medinaceli et al 2004), plant tissue type (Baraza et al
2004), and tissue quality (Murakami et al 2005).
The state park “Flor del Bosque” is a Natural Protected

6. Area (SEMARNAT-CONANP 2013–2018), located in Puebla
(Mexico), which has an oak forest. However, in recent de-
cades, increasing demand for firewood and clear cutting to
establish Eucalyptus spp. plantations have resulted in dra-
matic effects of fragmentation in the oak forests (Costes-
Quijano et al 2006). The given condition in the study area
is similar to other Natural Protected Areas that present some
degree of the environmental deterioration caused by land
use change, pollution, and habitat fragmentation (Cruz-
Elizalde et al 2015, Ochoa-Ochoa et al 2009). Given the pres-
ent condition of the study area, understanding Eucalyptus
edge effects on species interactions occurring within oak for-
est stands is of vital importance for conserving insect diver -
sity and oak native populations. The questions addressed in
this study included the following: (1) What are the primary
external herbivores of the Quercus species in a neotropical
temperate forest? (2) What is the Quercus-related effect of
proximity to Eucalyptus edges on external herbivory? (3)
Does external herbivory varies among seasons (dry and
rainy)? We hypothesized that insect herbivory associated
with Quercus would decrease away from Eucalyptus spp.
edges. It is expected that external herbivory will be higher
at the Eucalyptus spp. edge and will decrease gradually to-
ward the forest interior. In the study zone, most of the but-
terflies reproduce in the rainy season (Barranco-León et al
2016), so we expect higher herbivory in this season.
Materials and Methods
Study area
The Natural Protected Area “Flor del Bosque” is located in
the state of Puebla, Mexico (between 19°00′00″ and 19°01′
50″N, and 98°20′35″ and 98°20′53″W). The study area has
sub-humid temperate weather with rains during the summer
(June–September) while a markedly dry season occurs during

7. the rest of the year (Cwb in Köeppen classification), an an-
nual mean temperature of 18°C, and mean annual precipita-
tion of 800 mm. Relative humidity ranges from 42 to 67%
depending on levels of precipitation. The Natural Protected
Area covers a total of 664 ha of which 255 ha (41%, of the
total area of the protected area) is constituted by oak forest,
9.3 ha (1.5%) is covered Eucalyptus plantation, and the
Santin et al.
remaining 400 ha is covered mostly by pasture (Costes-
Quijano et al 2006).
Oak forests include 10 oak species (Badano et al 2010). In
general, forest patches found within the park are highly dis-
turbed and trees tend to be small in stature and highly
branched. The dense vegetation present in these areas gen-
erates more humid conditions and lower light availability,
and the dense forest cover prevents rainfall from reaching
the ground directly (Barranco-León et al 2016).
Eucalyptus patches are represented by two species,
Eucalyptus camaldulensis Dehnh and Eucalyptus globulus
Labillardière, which were introduced more than 45 years
ago. In contrast to oak forest patches, Eucalyptus stands
allow much higher levels of rainfall to reach the soil (81%)
and are characterized by greater light availability (Barranco-
León et al 2016).
Herbivore community
The main external herbivores that were observed feeding on
Quercus species were Lepidoptera. Internal herbivory was
also observed, done by insects that cause galls or mines. In

8. this study, we refer to just external herbivory caused by
Lepidoptera. From September 2009 to October 2010,
Lepidoptera caterpillars that were seen feeding on Quercus
spp. were collected and taken to the laboratory for observa-
tion until metamorphosis. In each case, the host tree species
was recorded. Caterpillars were reared at the Entomology
Laboratory of the Universidad de las Américas Puebla and
maintained at room temperature (20°C) and 60% relative
humidity. Within the rearing room, caterpillars were individ-
ually placed inside a 2.5-L plastic container or a plastic bag.
Old leaves fed to caterpillars were periodically replaced by
new leaves. Date of pupation was recorded for each cater-
pillar. When necessary, the containers were filled with a mix-
ture of dry leaves and dirt for the caterpillars to dig in and
pupate. After metamorphosis, adults were sacrificed for
identification. All Lepidoptera were identified to the mini-
mum taxonomic level possible using the proposed identifica-
tion keys from Borror and White (1970), Borror et al (1992),
Marshall (2006), Powell & Opler (2009), and mounted spec-
imens were revised by Ph. D Hantke and determined to
species. Oaks from which caterpillars were collected were
identified whenever possible to species using the
Rzedowski and de Rzedowski (2001) key for oaks.
Study design
Due to the fragmentation process that has occurred in the
park, the oak forest patches are of different size and border
Eucalyptus plantation or pastures. We selected three oak
forest patches (i.e., hereafter “sites”) that were bordering a
Eucalyptus plantation, to standardize for Quercus-Eucalyptus
border. In each site, we delimited three 20 × 20 m quadrants.
The quadrants were established at the edge (0 m from the
Eucalyptus stand), 30 m from the edge (intermediate zone),
and 60 m from the edge (forest interior).

9. Within each quadrant, we randomly selected five trees
each of Quercus castanea Née and Quercus obtusata
Bonpland. These two oak species were chosen because they
were abundant and/or its determination to species was pos-
sible. Determination of Quercus spp. was just possible for the
site two and three. The diameter at breast height of the oak
individuals selected range from 28 to 990 cm, with an aver -
age of 365 cm. For each tree, we harvested three branches
(maximum branch height of 5.5 m) and transported branches
to the laboratory for quantification of herbivory. This sam-
pling procedure was conducted during the first week of each
month, from February to October of 2010, which included
months of the rainy (June, July, August, and September) and
dry season (February, March, April, May, and October).
Leaf area and herbivory measurement
For each sampled branched per tree, we numbered 25 leaves
and randomly selected 15 to record the percentage of exter -
nal leaf herbivory. A total of 12,150 leaves were sampled,
1350 per month. To estimate herbivory, we calculated leaf
area by scanning each leaf and subsequently digitally recon-
structed the leaf (when there was tissue lost to herbivores)
using Paint software n.d. (version 6.1, Microsoft ®). This re-
sulted in estimates of area per leaf, one before and the other
after herbivore damage. We measured leaf area using the
program “Medición de objetos” version 4.2 (object ’s mea-
suring) (Ordiales-Plaza 1999–2000). The percentage of leaf
area consumed was estimated as actual or observed leaf
area/reconstructed leaf area prior to defoliation. For statisti-
cal analysis, we averaged leaf area and herbivory values
across leaves of all three branches sampled per tree, sepa -
rately for each survey.
Statistical analysis

10. We performed a linear mixed model analysis model testing
for the effects on herbivory (proportions) of distance to the
edge (border, 30 m, and 60 m to the edge) and season (rainy
and dry) as fixed effects and site and tree individual as ran-
dom factors, this last random factor accounts for the repeat-
ed measures in time. In the mixed model, one or more ran-
dom effects are added to the fixed effects. These random
effects essentially give structure to the error term “ε”. In our
study design, this resolves the non-independence that stems
from having multiple responses within the same site (Winter
2014). Response variables involving proportions are ade-
quately evaluated using a binomial distribution (Crawley
1993). All analyses were performed with the statistical
Eucalyptus Edge Effects on Quercus-Herbivore Interactions
software of the package “glmer” of the software R ver. 3.2.2
using binomial distribution (R Core Team 2015). Assumptions
of normality and homoscedasticity were evaluated with Q-Q
plot and fitted vs residuals. Significance of the factors was
evaluated using a likelihood ratio test which compares the
likelihood of two models: the model with the factor of inter -
est and the model without the factor of interest. Whenever a
factor was significant, we performed post hoc mean con-
trasts (Tukey method). A similar analysis was performed
but considering just the two sites in which the Quercus spp.
were determined. The response variable was herbivory pro-
portions, distance to the edge (border, 30 m, and 60 m to
the edge), season (rainy and dry), and Quercus species
(Q. castanea and Q. obtusata) as fixed effects and site and
tree individual as random factors.
Results

11. Herbivore community
A total of 70 caterpillars distributed across 24 morphospecies
were sampled from the oak trees sampled. Of these 70 spec-
imens, 43 pupated, and of these 28 completed their meta-
morphosis and developed into adults. The 24 morphospecies
sampled comprised 10 families of caterpillars, namely:
Arctiidae, Geometridae, Hesperiidae, Limacodidae,
Lymantriidae, Lasiocampidae, Megalopygidae, Noctuidae,
Riodinidae, Saturniidae. In addition, we also sampled one
morphospecies of beetle (Coleoptera: Coccinellidae). The
species that were identified were Emesis zeal Butler
(Riodinidae); Anisota assimilis Druce, Automeris cecrops
Boisduval, Automeris randa Druce, Paradirphia lasiocampina
R. Felder and Rogenhofer, (Saturniidae); Artace cribraria
Ljungh, Gloveria olivacea H. Edwards (Lasiocampidae);
Trosia obsolescens Dyar (Megalopygidae); Prolimacodes
badia Hübner (Limacodidae). These species were identified
or revised by Ph. D. Hantke. Of the collected morphospecies,
20 were found feeding on Q. castanea, four on Q. obtusata,
three on Q. laeta Liebman, and one on Q. laurina Bonpland.
Only three morphospecies were reported feeding on more
than one oak species.
Eucalyptus edge and season effect on leaf herbivory
We found significant effects of distance to the edge (X2 =
7.97, gl = 2, P = 0.018) and season (X2 = 6320.2, gl = 1,
P < 0.001) on the percentage of leaf herbivory, significant
two-way interactions among distance and season were
found (X2 = 530.7, gl = 2, P < 0.001). Specifically, we found
that the amount of herbivory at the forest edge (0 m) was
significantly lower than that found at the intermediate dis-
tance and the interior (t > 2.1, P < 0.02). With respect to

12. season differences, we found that in the rainy season the
amount of herbivory was significantly lower than that in
the dry season. A significant interaction between distance
and season, on herbivory, was found (X2 = 3.353, gl = 2, P =
0.187, Fig 1A). Interaction effect showed that the amount of
herbivory at the forest edge (0 m) was significantly lower
than that found at the intermediate distance and the interi -
or, but just during the rainy season (Tukey method,
P < 0.001). During the dry season, the same tendency was
found, but this was not significant (Tukey method, P > 0.30,
Fig 1A).
Analyses based upon the comparison of Q. castanea and
Q. obtusata for sites 2 and 3 showed that the percentage of
herbivory for Q. obtusata (6% ± 0.01) was significantly higher
than that for Q. castanea (4% ± 0.02) (X2 = 9.59, gl = 1, P <
0.002). The effects of the season (X2 = 3298.2, gl = 1,
P < 0.001) and the interaction among these two factors were
significant (X2 = 28.52, gl = 2, P < 0.001). For the interaction,
not significant differences were found among the herbivory
percentage of Q. castanea during the season with higher
herbivory (i.e., dry) and Q. obtusata during the season with
lower herbivory (Tukey method, P = 0.452). The other com-
parisons were significant (Tukey method, P < 0.007, Fig 1B).
Discussion
This study describes the community of herbivores associated
with the oak species of native forest in the Neotropics and
evaluates the effect of the distance to the edge and season
on herbivory. The oak herbivorous community was mainly
composed of lepidopterans, and we found greater herbivory
at the interior of the forest, which may be related to specific
microclimatic conditions at the interior of the forest or to the
presence of a specialist Lepidoptera community. However,
this pattern was significant just during the rainy season, al -

13. though the higher amount of herbivory was found during the
dry season. Contrary to what was expected, herbivore levels
were not higher at the Eucalyptus edge, and this result may
be explained by the idiosyncratic characteristics of the lepi -
dopteran community associated to the oak forest (i.e., spe-
cialist species). We discuss in detail the results of this study.
All of the families to which the insect specimens were
sampled, except Coccinellidae, are constituted exclusively
by Lepidoptera herbivorous species. In addition, the
Noctuidae family has been previously reported as one of
the most important groups associated with Quercus species
(Monreal et al 1992, Hochwender et al 2003, Extremera et al
2004). Of lesser importance but also previously reported for
oaks are Lymantriidae (Monreal et al 1992, Extremera et al
2004) and Lasiocampidae family (Monreal et al 1992). The 24
morphospecies recorded, which belonged to 10 families, in-
dicate a high diversity of lepidopteran herbivores that feed
Santin et al.
and possible depend in an important way of the Oak species
in the zone. This diversity agrees with the high diversity
found by Barranco-León et al (2016) for diurnal lepidopteran
species, in the same study zone, who found 91 species
contained in the six taxonomic families of diurnal lepidop-
terans. Barranco-León et al (2016) point out that the diversity
found in the park reserve is greater than the one reported in
larger forest ecosystems in Mexico.
We found that levels of herbivory on oak plants decreased
significantly at the edge of Eucalyptus stands relative to
plants located in the quadrants inside forest patches. This
pattern indicates that Lepidoptera herbivores are negatively

14. affected by proximity to a border Quercus-Eucalyptus. This
result contrasts with the findings of De Carvalho Guimarães
et al (2014), who found higher herbivorous levels at the edge
than at the interior of temperate forests. They attributed this
result to an increase in plant abundance in edge habitats, as
the key mechanism, leading to an increase in herbivorous
levels. However, De Carvalho Guimarães et al (2014) point
out that this explanation would apply to a generalist herbiv-
orous community; meanwhile, a specialist herbivorous com-
munity would not be favored by an increase in this plant
abundance as much of them would belong to unpalatable
plant and/or replace their local host. In this study, the
Lepidoptera herbivores probably are oak specialist, for which
the Eucalyptus edge represents a degraded habitat of lower
resource quality. Santos & Benítez-Malvido (2012) found a
similar result to ours; they evaluated the caterpillar herbivory
damage on Heliconia latispatha, and they found that herbiv-
ory levels diminished from 4.2% in forest gaps to 0.5% on
road edges. They attributed this result to changes in micro-
climatic conditions, host quality (higher physical vs. chemical
defense on edges), and local abundance of herbivores (lower
caterpillars abundance, due to higher predation pressure
and/or dispersal limitation on edges).
Microclimatic conditions could explain the differences in
herbivory levels between the edge and the forest interior. In
the study zone, Barranco-León et al (2016) reported higher
temperatures and photosynthetic active radiation (light) in
the Eucalyptus plantation than in the oak forest; meanwhile,
the humidity was higher in the oak forest. We argue that
Quercus herbivores are not favored by greater light availabil -
ity; this result is similar to that reported by Baraza et al
(2004) with Quercus seedlings, who found that plants grow -
ing in the shade had lower levels of chemical defenses than
did sun-grown plants, making them more attractive to her-

15. bivores. Related to this pattern is the study of Connor (2006)
who found that survival rates for species of Lepidoptera de-
creased with increasing light availability probably due to dif-
ferences in foliage quality (Connor 2006). In our study, mild
temperatures and higher humidity, at the interior of the oak
forest, especially during the Lepidoptera reproduction period
(rainy season), could favor them preventing egg desiccation
and promoting larvae development (Barraco-Leon et al
2016). The negative effect of Eucalyptus edge on
Lepidoptera herbivory community could be accentuated
more in the reproductive period of the Lepidoptera and ex-
plains why is in this season that we found a significant effect
of the distance to the edge. However, our findings disagree
with other studies reporting that herbivory is favored by
increasing light availability at forest edges (Lincoln &
Mooney 1984, Moore et al 1988, Basset 1991, but see
Medinaceli et al 2004, Connor 2006, Rossetti et al 2014,
Pereyra et al 2015).
The degree of host specificity of the caterpillar species
associated with Quercus could also explain the herbivorous
pattern observed. The comparison of herbivory on
Q. castanea and Q. obtusata indicated that the latter was
more heavily attacked. We speculate that Q. castanea is of
higher quality (fewer defenses or higher nutrient content)
than Q. obtusata and is thus preferred by the sampled spe-
cies of Lepidoptera. Quercus obtusata might have specialist
Lepidoptera that caused more damage than the greater but
less specialist Lepidoptera community associated to
Q. castanea. Similarly, Maldonado-López et al (2016) found
that gall wasp richness depended on the Oak species
considered.
0
2

16. 4
6
8
10
A
B
0 m 30 m 60 m
H
er
bi
vo
ry
p
er
ce
nt
H
er
bi
vo
ry
p

17. er
ce
nt
Distance from Eucalyptus edge
Dry Rainy
0
1
2
3
4
5
6
7
8
9
Q. castanea Q. obtusata
Quercus species
a
c
a
b
a
b
a

18. b
c
a
Fig 1 A Edge effect on the percent of leaf area lost to
Lepidoptera
herbivores on oak for the dry and rainy season (mean herbivory
percent ± se) (Quercus spp.). Herbivory percent was
significantly lower
on edge in comparison with the oak forest interior (30 m and 60
m), but
just during the rainy season. B Mean herbivory percent for the
two
Quercus species considered (Quercus castanea and Quercus
obtusata,
sites 2 and 3). Different letters (a, b, c) indicate significant
differences
(Tukey method, P < 0.001).
Eucalyptus Edge Effects on Quercus-Herbivore Interactions
The idea of specificity of the caterpillar species associated
with Quercus is in accordance with the findings done by
Barranco-León et al (2016), who studied lepidopteran com-
position in the area and considered the three different types
of vegetation within the reserve (oak forest, grassland, and
Eucalyptus plantation). They found that lepidopteran diurnal
species, mainly specialist species, were associated with oak
forest; meanwhile, no positive correlation (i.e., the observed
frequency of the registered lepidopteran species were not
bigger than that of expected by random) were found be-

19. tween the Eucalyptus plantations and any lepidopteran spe-
cies, even though a number of butterflies species were re-
corded in this type of vegetation. They concluded that al -
though Eucalyptus plantations could be used as corridors
by the butterflies, this type of vegetation was not essential
for preserving native lepidopteran species.
We also found evidence of seasonal variation in the levels
of herbivory, as indicated by significant lower herbivory dur -
ing the rainy season. In the zone, Quercus trees shed their
leaves in March, so the lower levels of herbivore found dur -
ing the rainy season correspond to herbivory on the new
leaves; meanwhile, a greater herbivore level damage was
found during the dry season, which corresponds to herbivor y
on older leaves. This contrasts with other communities in
which young leaves feeders represent an important compo-
nent of the Lepidoptera community (Forkner et al 2008).
However, these results are consistent with the lepidopteran
seasonality found for the lepidopteran community in the
area, for which it is reported a higher diversity of forest oak
Lepidoptera specialists as well as generalist, during the dry
season (specialist 33 species in the rainy season vs 39 species
during the dry season, generalist 20 species vs 30, respec-
tively (Barranco-León et al 2016)). Similarly, Maldonado-
López et al (2016) found a richer gall wasp community during
the autumn than during the spring in an oak forest in Mexico,
associated with a higher quantity of leaves in this season.
This study highlights the negative effects of the proximity
of an oak forest edge to Eucalyptus spp. stands. Border effect
could be resulting in higher levels of herbivory inside forest
patches, and this in turn could lead to reductions in Quercus
spp. growth and survival. The effect of insect herbivory on
plant growth and survival will depend on the level of herbiv-
ory, the leaf value (e.g., old vs new leaves), and the host
condition (Schowalter et al 1986, Rossetti et al 2014).

20. Previous work has shown that levels of herbivory over 20%
cause a decrease in reproductive success for Q. alba Linneo
and Q. robur Linneo (Crawley 1985, Hochwender et al 2003).
Given that forest edge effects will likely become more impor -
tant with increasing levels of fragmentation, we argue that
further work is necessary in order to uncover the mecha-
nisms by which fragmentation and the edge effects shape
Quercus-herbivore interactions and the consequences of
such changes for oak survival and recruitment, as well as
for insect abundance and diversity. Future work should ad-
dress the consequences of changes in herbivory due to edge
effects on oak survival rate and seed germination.
We found evidence for edge effects on insect leaf damage
associated with oaks. We found that leaf herbivory was low-
er at the forest edge relative to the interior, a finding which is
consistent with the scenario of a rich site neighboring a de-
graded one (Ries & Sisk 2004). However, this effect was just
found in the rainy season, which may be related to the re-
production period of the principal herbivorous found: larvae
of Lepidoptera, which probably prefer the mild temperatures
and higher humidity, at the interior of the oak forest. Some
of the caterpillar morphospecies sampled could be special-
ized on Quercus spp., although further research is necessary
to characterize the degree of dietary specialization of these
herbivores. Further work is also needed to determine if ob-
served levels of herbivory are affecting oak survival, recruit-
ment, and reproduction. Research should also focus on de-
signing strategies aimed at reducing the negative effects of
forest edges on oak populations. Some of these strategies
could be aimed at re-establishing and maintaining balanced
plant-herbivore interactions as well as re-introducing native
oak species. The prevalent conditions in this park are similar
to those faced by most protected areas: a natural conserved
is within a matrix, or/and bordered by fragmented vegeta-

21. tion, so strategies must be searched for improving and main-
taining biodiversity within these areas.
Acknowledgments This work was supported by Fondo Mixto
Consejo
Nacional de Ciencia y Tecnología - Gobierno del Estado de
Puebla (grant
number PUE-2008-1-108571) to Ernesto I. Badano. The
Administration of
the State Park and Ecological Reserve Lázaro Cárdenas del Río
“Flor del
Bosque” granted permission to carry out the study and provided
logistic
support.
Authors’contributions This work is the result of the bachelor’s
thesis
of CHS. CHS, MC, GGJ, and EIB planned and designed
experimental
work. CHS, MNBL, FLC, MC, and GGJ executed experimental
work.
MNBL and FLC realized Lepidoptera collection and breeding.
CHS and
MC conducted data analyses and wrote the manuscript. CHS,
MC,
MNBL, GGJ, EIB, and FLC revised and made contributions to
the
manuscript.
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1
Lab 10 Forest Edge Effect (Data Analysis)
Objectives:
between forest edge
and interior habitats at BOLOS.
richness and canopy
cover.
and canopy cover.
cover.
cover.
Background Information

35. To compare the abundance and species richness (α diversity) of
arthropods between
forest edge and interior habitats, we will use analysis of
variance (ANOVA). Although
fairly robust, this method makes some assumptions about the
data, so we need to test
those assumptions about our data first.
1. What are some of the assumptions of ANOVA and how can
they be tested?
To examine the relationship between the species richness of
arthropods and some
environmental characters (e.g., canopy cover %), we will use
simple linear regression.
This statistical method analyzes the statistical relationship
between two quantitative
variables (predictor and response) with hypothesized causality
between them (Fig.
10.1).
2

36. A simple linear regression model
represents the relationship
between the mean (expected
value) of the response and the
predictor by the function
μy = a + bx,
where x is the predictor, y is the
response, and a is the intercept.
Notice that y does not always
equal to a + bx. Rather, the
observations have variations
around the regression line and
their mean (μy) is given by the
function.
A linear regression model makes a
few assumptions:
1. The mean of responses (μy) at each predictor value (xi) is
described by a
linear function of xi.
2. The errors of responses are independent.
3. The errors of responses at each predictor value are normally
distributed.
4. The errors of responses at different predictor value have
equal variances
(σ2).
Sometimes the linear regression relationship between the
predictor and response

37. entails transformation of both variables. A common
transformation is the log10
transformation, which gives the data points a better fit to the
linear regression model.
We will model the abundance of arthropods by the canopy cover
percentage using
simple linear regression in R. You will then plot the two
variables and draw the least
squares linear regression line.
2. What is α (alpha) diversity?
3. Which variable is the predictor? Which variable is the
response?
Fig. 10.1. Liner regression between predictor (x) and response
(y).
https://cdn-images-
1.medium.com/max/1600/1*LEmBCYAttxS6uI6rEyPLMQ.png
3
Activity
Work in groups, download the OneDrive spreadsheet as an
Excel file. Next, import the

38. data into R, using RStudio. Be sure to select the correct sheet
from your Excel file, and
give it a concise name that’s easy to type with no spaces (e.g.,
yourDF). You can view
your data frame by clicking on it in the RStudio Environment.
We first need to create two new variables in our data frame, the
α (alpha) diversity and
total abundance for each cover board (row). Use this line of
code to create a column
named “Alpha”:
yourDF$Alpha <- rowSums(yourDF[,c(9:21)]>0)
Use this line of code to create a column named “Abundance”:
yourDF$Abundance <- rowSums(yourDF[,c(9:21)])
Now let’s test for the normality and homogeneity of our data.
We will first test normality
using Q-Q plots. We will do this for both alpha diversity,
qqnorm(yourDF$Alpha)
qqline(yourDF$Alpha)
and abundance.
qqnorm(yourDF$Abundance)
qqline(yourDF$Abundance)
Normally distributed data plots should look something like Fig.
10.2. Any major
deviations from the line suggest non-normality.

39. We will then test the homogeneity of the
variances our data using the Bartlett Test.
bartlett.test(Abundance~Habitat, data = yourDF)
The hypotheses tested by the Bartlett test are:
H0: σ12 = σ22 = ... = σk2
Ha: σi2 ≠ σj2 for at least one pair (i,j).
H0 is rejected if p < 0.05. Fig. 10.2. Q-Q plot of normally
distributed data.
4
To perform ANOVA, use the R function aov().
yourmodel1 <- aov(Alpha ~ Habitat, data = yourDF)
summary(yourmodel1)
yourmodel2 <- aov(Abundance ~ Habitat, data = yourDF)
summary(yourmodel2)
4. What are the p-values for each model?

40. 5. Is the null hypothesis rejected for each metric (alpha
diversity and abundance)? Why
or why not?
Next, we will perform the linear regressions of alpha diversity
and abundance based on
canopy cover. However, it turns out that R does not like the
“%” character in the title of
the “Canopy_cover_%” column of the data frame, so let us fix
that first. We will do so by
making a new column in our data frame with a simplified title
“Canopy” and copy the
values from the original column. Use this line of code:
yourDF$Canopy <- yourDF$`Canopy_cover_%`
To construct simple linear regression model on the predictor
and response variables,
use the lm() function. First, construct the model for alpha
diversity:
canopyreg1 <- lm(Alpha~Canopy, data = yourDF)
Then show results of the regression using the summary()
function.
summary(canopyreg1)

41. 5
6. What are the p-values for the intercept and the predictor
(canopy)? Is this model a
good fit for the data? Why or why not?
7. What is the linear function of this simple linear regression
model?
Now plot the transformed variables and draw a regression line
through the data points.
Use the following codes:
attach(yourDF)
plot(Canopy, Alpha, xlab = “Canopy cover %”, ylab = “no. of
species”)
abline(lm(Alpha~Canopy), col = “red”) #drawing regression
line
Save a copy of your plot. Does the regression line look like a
good fit?

42. Repeat the linear model construction and graph plotting for
arthropod abundance
against canopy cover. Copy the R codes that you used below:
6
References
Engineering Statistics Handbook. Bartlett’s Test.
https://www.itl.nist.gov/div898/ha ndbook/eda/section3/eda357.h
tm
Pardoe, I. 2018. STAT 501 Online course material website. The
Pennsylvania State University.
https://newonlinecourses.science.psu.edu/stat501/
Quick-R. Assessing Classical Test Assumptions.
https://www.statmethods.net/stats/anovaAssumptions.html
Sokal, R. R. and F. J. Rohlf. 1995. Biometry: the principles and
practice of statistics in biological research.
W. H. Freeman and Company, New York, NY. 887 p.

43. 7
Scientific Research Paper
You will write a lab report using the scientific format of
introduction, methods, results,
and discussion to report the findings of this lab. You need to
search the literature on
edge effects for your introduction and to support or to compare
with your conclusions for
the discussion section of your paper (citing your literature as
shown in the format given
to you previously).
Things to think about in your paper:
Why are the potential factors causing differences in species
richness and/or abundance
between edge and interior habitats? What are some of the things
that explain this
difference from the literature?
Why was canopy cover presumed to have an effect on the
species richness and
abundance of arthropods in the forest? What other data that you
collected might be
useful in analyzing the arthropod species distributions? How

44. would you analyze them?
If you had null results (no significant difference between
habitats and/or no strong
correlations) for your experiment, what are the potential
reasons?
What are the differences, if any, in the types of species and
their population sizes that
occur in the two different habitats? How would you analyze
this? Suggest some
possible statistical analyses in the discussion section.
Potential literature sources:
Murcia, C. 1995. Edge effect in fragmented forests:
implications for conservation.
Trends in Ecology and Evolution 10:58-62.
Hernández-Santin, C., M. Cuautle, M.N. Barranco-león, J.
García-Guzmán, E.L.
Badano, F. Luna-Castellanos. 2019. Eucalyptus edge effect on
Quercus-herbivore
interactions in a Neotropical temperate forest. Neotropical
Entomology.
https://doi.org/10.1007/s13744-019-00694-5
8

45. Research Paper in Ecology
Forest edge effect on species richness and abundance of
arthropods at BOLOS
Scoring Rubric
Introduction (20 pts)
effect?
Methods and Results (25 pts)
materials and methods used to
gather data.
depict species
numbers in different habitats.
whether there is significant difference in
arthropod distribution between forest interior and edge habitats.
omputed and used to draw best
fit line between the plots.
Discussion and Conclusions (35 pts)
or refute the edge effect on

46. arthropod community patterns.
ted research on the concept of
edge effect.
(that arthropod species richness and
abundance are or are not affected by edge effect).
Grammar and Mechanics (10 pts)
r spelling does not detract from the
paper.
Literature Cited (10 pts)
primary literary sources