Activity Patterns, Intergroup Encounters, and Male Affiliation in Free-Ranging Bearded Sakis (Chiropotes sagulatus)

The assessment of how primates divide their daily activities is one of the foundations of primate behavioral ecology but the activity patterns and social behavior of the Pitheciines, including bearded sakis (genus Chiropotes), are poorly understood. During a 15-mo study, I collected 560 h of data on subgrouping, activity patterns, social behavior, and intergroup encounters of a group of free-ranging Guianan bearded sakis (Chiropotes sagulatus) in Guyana. The study group consisted of at least 65 individuals but showed a high degree of flexibility in grouping patterns (mean group size 39 ± 10). They were highly active, spending ca. 70% of their diurnal activity budget traveling and feeding. Activity patterns were relatively consistent throughout the year, although time spent feeding correlated significantly with fruit availability. The most common social behaviors were social resting and grooming. Agonism was rare (2.56% of social behavior) but did occur in the context of intergroup encounters, with males from the same group cooperating in intergroup agonism. Bearded sakis showed a high level of within group male affiliation, with male–male partners making up 65% of grooming dyads and males having another male as their nearest-neighbor 66% of the time. These results show that bearded sakis are characterized by egalitarian male–male and male–female relationships, highly fluid group sizes, and high levels of male affiliation. Similarities in the social behavior of bearded sakis and muriquis suggest several possible explanations for male–male bonding including cooperative defense of females from other groups, kinship, and maintenance of social cohesion after subgroup coalescence.     

Gis analysis of patch use and group cohesiveness of bearded sakis (chiropotes sagulatus) in the upper essequibo conservation concession,guyana

This study examines how northern bearded sakis (Chiropotes sagulatus) in Guyana adjust group cohesiveness according to the distribution and quality of food patches. I introduce a GIS based method for quantifying food patch quality and how it relates to bearded saki group spread and group size. While the concept of food patch is central to most models of primate socioecology, defining what constitutes a patch has been notoriously problematic in primate studies. In addition, researchers have struggled to quantify group spread and group cohesiveness. Advances in spatial analysis software in the last decade now allow primate researchers to better quantify these variables. Group spread in bearded sakis was not significantly greater in lower quality patches and sakis were not more spread out during feeding than during other activities. However, the study group was significantly less spread out during social behavior. Bearded saki group size was significantly correlated with both monthly fruit abundance and patch quality. In fact, mean daily patch quality explained ～40% of the variation in foraging party size. These results suggest that bearded sakis may rely on a highly fluid social structure to mitigate the effects of intragroup feeding competition while living in large groups. Sakis do not adjust group spread on a patch‐by‐patch basis but rather fission into smaller foraging parties when resources become scarce seasonally and patch quality is low. This study shows that GIS is a powerful tool for modeling the relationship between group cohesiveness and resource quality and distribution. Am J Phys Anthropol, 2013. © 2012 Wiley Periodicals, Inc.     

Long-term Study of Group Dynamics and Female Reproduction in Venezuelan Pithecia pithecia

White-faced sakis (Pithecia pithecia) are well known for their specialized feeding strategy and dependence on seed-eating, but we know less about social dynamics and reproduction. I summarize data from 1990 to 2001 on sakis inhabiting a small island in Lago Guri, Venezuela that includes changes in group composition, aggressive behavior, and female reproductive histories. Though the characteristic group size and typical mating system are still uncertain for wild, free-ranging Pithecia spp., size of the study group ranged from 2–3 adult females and 1–4 adult males. My group and I collected fecal samples from adult females, which we dried and assayed for estrogen (E₁C) and progesterone (PdG) conjugates to document reproductive cycles and female development. During the study, as many as 3 females were either cycling or pregnant at the same time. Ten infants were born during the study, 4 of which survived to adulthood. Five interbirth intervals after weaning an infant ranged from 12 to 36 mo. Though researchers often assume Pithecia spp. are monogamous, multiple breeding females can coexist in groups without evidence of reproductive suppression. Within the pitheciine clade, Pithecia spp. exhibit a mosaic of behavioral and morphological traits intermediate between bearded sakis and uakaris on the one hand and their sister-group, the pair-bonded titis, on the other.     

Seed predation by monkeys and macaws in eastern Venezuela: Preliminary findings

Feeding data collected concurrently on bearded sakis (Chiropotes satanas) and red and green macaws (Ara chloroptera) on a large island in Guri, Venezuela provides preliminary evidence that these two seed predators have similar diets. Individuals of both species were equally capable of opening very hard, protected fruits. Of the seven fruit species used by macaws during the study period, four species were also ingested by sakis at the same stage of ripeness, two species were ingested at different stages of ripeness (macaws earlier than sakis), and one species was never observed to have been eaten by sakis. The second finding, that macaws ingest young seeds of the Anacardiaceae and Burseraceae families and the bearded sakis ingest only the ripe mesocarp of these species suggests that the most distinguishable difference in their diets might be a tolerance of toxins by the macaws that act as feeding deterrents for the monkeys. Although we did not document the location of local clay licks in eastern Venezuela, the use of clay licks by macaws in Peru (Munn, 1992) suggests that this activity (that is not practiced by the sakis) may be helpful in detoxifying or ameliorating the effects of ingesting chemically protected fruit. deceased.     

Diet of a free-ranging group of squirrel monkeys (Saimiri sciureus) in eastern Brazilian Amazonia

The feeding behaviour of free-ranging Saimiri sciureus was monitored over a 6-month period in eastern Brazilian Amazonia. Behavioural data were collected in scan samples (7-9 days per month), and fruit and arthropod availability were recorded monthly. A total of 3,546 feeding records were collected, divided between reproductive plant parts (55.1%) and arthropods (44.9%). The majority of identified prey were orthopterans and lepidopterans, and 10 of the 23 plant species exploited were Leguminosae and Sapotaceae. The diet varied progressively between August (20.0% plant, 80.0% animal) and January (79.7% plant, 20.3% animal). This shift accompanied an increase in the number of fruiting trees and evidence of declining arthropod availability. This included a marked reduction in foraging success and increasing consumption of immature prey. Overall, the data indicate that Amazonian squirrel monkeys may be relatively frugivorous during periods when prey is scarce.     

Geophagy at termitaria by bearded sakis (Chiropotes satanas) in Southeastern Brazilian Amazonia

Geophagy is rare in primates, but has been recorded in a variety of platyrrhine genera. The first observation of geophagy in bearded sakis (Chiropotes satanas) is reported here. Two bouts were recorded during long-term monitoring of a free-ranging group inhabiting a small island in a reservoir in eastern Brazilian Amazonia. On both occasions, soil was obtained systematically from a termitarium in the crown of an Eschweilera coriacea tree. Both events occurred during the late dry season. Although there is no evidence of any significant shift in foraging behavior during this period, it is possible that soil ingested provided an essential mineral supplement to a diet limited by the small size of the island.     

Pithecia pithecia's behavioral response to decreasing fruit abundance

In this article we describe the behavioral responses of a group of white-faced sakis' (Pithecia pithecia) to fruit and water scarcity. Six sakis were observed on Round Island in Guri Lake, Venezuela, between March and May 1996. These months are considered the dry season and the beginning of the wet season. Sakis specialize in eating seeds. During the present study only one tree species, Licania discolor (Chrysobalanaceae), fruited in substantial numbers. Licania seeds accounted for 88% of the time the sakis spent eating fruit in March, 87% in April, and 80% in May. We estimate that the sakis' intake of Licania seeds dropped from 2,573 seeds in the 15-day observation period in March to 956 seeds in the 16-day observation period in May. The sakis not only spent less time eating Licania, they ate the seeds at a much slower rate. The drop in the sakis' feeding rate was probably due to increased local search and inspection times. In response to the scarcity of fruit, the sakis ate more young leaves, insects, and flowers. Feeding bouts became more frequent but shorter. Mean distances between feeding bouts fell significantly and the sakis revisited trees less often.     

Seasonal and taxonomic aspects of the size of arthropods in the tropics and its possible influence on size-selectivity in the prey of a tropical spider community

Summary During one year in Panama the size (=body length) of arthropods (representing the potential prey of a spider community) was determined by sampling with pitfall traps, bowl traps and sweep-netting. Most arthropods found were small and the distribution of their size is considerably skewed to the left (Figs. 1, 2). Pitfall traps and bowl traps yielded similar results but sweep-netting collected larger arthropods and may be size-selective. Although the variation of arthropod size is high, no seasonal influence on body size could be detected in the main prey groups of spiders (Figs. 3, 4). Differences in the size spectra of the actual prey of a tropical spider community are therefore not caused by seasonal variations in the availability of particular prey size classes. Species-specific prey size spectra, however, may be dependent on properties of the webs concerned, microhabitat selection or other, e.g. physiological or ethological differences between the spider species.     

ARTHROPODS THAT PREY ON VERTEBRATES

1. Many arthropods are predators of vertebrates: four orders of the class arachnida, six orders of insecta, five orders of crustacea and one order of chilopoda include species that have been reported to eat vertebrates. At the population level, some arthropods are responsible for significant mortality among some vertebrates.
2. Arthropods are well equipped for this type of predation; many are larger than vertebrates (approximately 20% of the vertebrate fauna of eastern North America is less than 10 cm in length), they may hunt in social groups and many have toxins or other adaptations that increase predatory efficiency.
3. Several arthropod predators and vertebrates may be involved in cross predation, the species eating each other. The switch in the role of predator and prey occurs during 'ontogenetic reversal' as the vertebrate grows from small and vulnerable to large and predaceous. Cross predation decreases the future risk for one's self or offspring.
4. The opportunity for arthropod predation on vertebrates exists in many communities, but a review of some food webs catalogued by Cohen (1978) indicates that this particular link may be easily overlooked. Some arthropods should be investigated as potential predators of vertebrates.
5. The information available from the analysis of feeding interactions in a community should be an important link between field and theoretical ecology; however, most food webs are probably underestimates of the complexity that is commonplace.     

Ecological Correlates of Ranging Behavior in Bearded Sakis (Chiropotes sagulatus) in a Continuous Forest in Guyana

Group size and the distribution and quality of food resources are among the most important determinants of primate ranging behavior. In this study, I use the framework of the ecological constraints model to assess correlates of range size of a free-ranging group of bearded sakis (Chiropotes sagulatus). Bearded sakis are among the widest ranging neotropical primates, yet the lack of data from continuous forest populations has made understanding the factors influencing such large ranges difficult. I collected data on ranging behavior and diet during 44 full-day follows over 15 mo. The focal group used a home range of ca. 1000 ha and had daily path lengths of 2.8–6.5 km (mean?=?4.0 km). Daily path length did not significantly correlate with group size, patch quality, food availability, or the spatial distribution of feeding trees. Monthly home range size significantly positively correlated with group size and patch quality. The focal group had significantly shorter paths when ripe fruit consumption was higher and had more diverse diets, visited more food patches, and used larger monthly home ranges when they consumed a higher percentage of seeds. The results of this study, combined with other recent studies of Chiropotes in continuous forest, suggest that large home ranges (approaching 1000 ha) are characteristic of the genus. Although range size may be related to group size and food patch size, I suggest nutrient mixing and the need to balance the effects of seed secondary compounds as additional explanations for the large ranges of bearded sakis.     

Seasonal insectivory by Black‐headed Trogons,a tropical dry forest frugivore

ABSTRACT Fruit‐eating birds are important seed dispersers in tropical forests, but little is known about the extent to which they rely on insects or how their diets vary seasonally. We used field observations of focal adults to quantify the diets of adult and nestling Black‐headed Trogons (Trogon melanocephalus) at nine nests in a lowland dry forest in Costa Rica. From May 2004 to August 2004, we documented 540 food deliveries to nests and 1080 food items consumed by adults. Adult and nestling trogons were largely insectivorous, feeding mainly on moth caterpillars (Lepidoptera). Fruit accounted for only 10.5% of items consumed by adults and 2.2% of items delivered to nestlings (6.1% and 0.6% of estimated dry mass, respectively). Adult and nestling diets differed significantly in both composition and prey size, with adults consuming more fruit and fewer large insects (Phasmatodea and Mantodea) than nestlings and eating more types of arthropods and fruit. Although both adults and nestlings relied heavily on moth larvae, adults preferentially consumed small caterpillars and delivered large ones to their nestlings. In addition, the proportion of large caterpillars delivered to nests remained constant throughout the nestling period, whereas the proportion of large caterpillars eaten by adults declined significantly with nestling age. Overall, arthropods delivered to nests averaged 70% heavier than those consumed by adults (estimated dry mass). Our results suggest that Black‐headed Trogons time reproduction to coincide with arthropod rather than fruit abundance, a pattern that may be more common among omnivorous forest birds than previously recognized.     

High‐throughput sequencing of fecal DNA to identify insects consumed by wild Weddell's saddleback tamarins (Saguinus weddelli,Cebidae, Primates) in Bolivia

The genus Saguinus represents a successful radiation of over 20 species of small‐bodied New World monkeys. Studies of the tamarin diet indicate that insects and small vertebrates account for ～16–45% of total feeding and foraging time, and represent an important source of lipids, protein, and metabolizable energy. Although tamarins are reported to commonly consume large‐bodied insects such as grasshoppers and walking sticks (Orthoptera), little is known concerning the degree to which smaller or less easily identifiable arthropod prey comprises an important component of their diet. To better understand tamarin arthropod feeding behavior, fecal samples from 20 wild Bolivian saddleback tamarins (members of five groups) were collected over a 3 week period in June 2012, and analyzed for the presence of arthropod DNA. DNA was extracted using a Qiagen stool extraction kit, and universal insect primers were created and used to amplify a ～280 bp section of the COI mitochondrial gene. Amplicons were sequenced on the Roche 454 sequencing platform using high‐throughput sequencing techniques. An analysis of these samples indicated the presence of 43 taxa of arthropods including 10 orders, 15 families, and 12 identified genera. Many of these taxa had not been previously identified in the tamarin diet. These results highlight molecular analysis of fecal DNA as an important research tool for identifying anthropod feeding patterns in primates, and reveal broad diversity in the taxa, foraging microhabitats, and size of arthropods consumed by tamarin monkeys. Am J Phys Anthropol 156:474–481, 2015. © 2014 Wiley Periodicals, Inc.     

Arthropods within the woody element of hedgerows and their distribution pattern

1 The diversity and abundance of arthropods within hedgerows was investigated using insecticide fogging. In total, 13 390 arthropods were collected from 181 m³ of hedge (2% of the total volume). The taxonomic diversity of the total sample included 51 families in 13 orders, all within the phylum Arthropoda. Five orders accounted for 90% of all arthropods: Araneae, Coleoptera, Diptera, Hemiptera and Hymenoptera. The predators were the dominant functional group accounting for 40% of the total sample. 2 The linear distribution of hedgerow arthropod assemblages was investigated by sampling arthropods in 13 hedges at seven equidistant points along each hedge. Abundance of most arthropod taxa and the four functional groups (predators, parasitoids, herbivores and scavengers) consistently showed a clumped distribution along hedges, with high numbers at both ends and in the middle section. Hedge ends were defined either as a node, where the hedge intersected with another hedge, or as a gateway prior to an adjacent landscape feature such as a wood. Aggregation of arthropods at the nodes may reflect preferable microclimatic conditions at hedgerow junctions, whereas aggregation at a gap suggests the gap acted as a barrier to movement. The aggregation at the centre remains unexplained but may be a manifestation of the movement of individual arthropods along the hedgerow. 3 The great abundance and diversity of arthropods found in the present study emphasizes the status of hedges as one of the most important noncrop habitats on farmland. The arthropods that they contain may act as food for other farmland species, aid pest control and contribute to crop pollination.     

Arthropods associated with the crown of Mauritia flexuosa (Arecaceae) palm trees in three different environments from Brazilian Cerrado

Canopy arthropods, mainly from palm trees, are little known in the Brazilian Cerrado. In order to describe the arthropod community structure associated with the crown of Mauritia flexuosa (Arecaceae), we sampled 150 palm trees in six "veredas" of the Federal District, Brazil, in wild, rural and periurban areas in the rainy season. The arthropods within abandoned bird nests, mammal refuges, leaves and organic matter were manually collected, preserved in ethanol 70% and separated by order, family, morphospecies and feeding guilds. Stem height and diameter of the palm crowns were measured and leaves and bird nests were counted. We collected 3,862 arthropods, from 15 orders, 45 families and 135 morphospecies. The most abundant orders were Coleoptera (28.6%), Blattodea (21.8%), Collembola (11.4%) and Hemiptera (10.2%). The families Blaberidae, Entomobryidae, Reduviidae, Oniscidae, Staphylinidae, Carabidae and Formicidae, represented 82.1% of all individuals collected. The majority of morphospecies was not abundant, 71 (52.6%) were represented by less than 1 individual/tree. Coleopterans accounted for the highest number of morphospecies (43.7%) followed by Araneae (20.0%). The analysis of the arthropod feeding guilds showed prevalence of predatory/hematophagous ones (36.0%). Arthropod richness and abundance presented smaller values for periurban environment. The number of bird nests presented positive correlation with abundance and richness; this was not found when considering the measurements of the palm trees. The importance of M. flexuosa for the maintenance of the arthropod fauna of the "veredas" in Cerrado biome is discussed.     

Nutritional composition of the preferred prey of insectivorous birds: popularity reflects quality

Food availability is emerging as a key determinant of avian occurrence and habitat use in a variety of systems, but insectivores have received less attention than other groups and the potential influence of nutritional quality has rarely been considered. Rather than a uniform food source, arthropods vary greatly in terms of nutritional composition, but does this variation translate into differential consumption? Building on previous work that demonstrated clear preference for some arthropod groups by 13 species of ground‐foraging insectivores, we compare the nutritional composition of these arthropod groups with other groups commonly encountered but seldom consumed in the same habitat types. Using samples of arthropods collected from a eucalypt woodland in southern Australia, we found the high frequency prey groups (Coleoptera, Lepidoptera, Orthoptera and Araneae) consistently contained higher fractions of crude protein and total fat than the low frequency groups (Diptera, Hymenoptera and Odonata). Even more clear‐cut differences were noted in terms of micronutrients; high frequency prey containing significantly greater concentrations of seven elements than low frequency prey and significantly greater amounts per individual arthropod for all eleven elements measured. These results indicate that the nutritional quality plays an important role in prey selection in insectivores and suggests that micronutrients may be more important determinants of prey choice than previously recognized. Integrating these findings with previous work suggesting food limitation may constrain distribution patterns of birds in fragmented landscapes, we contend that variation in nutritional quality helps explain observed patterns in insectivore diets and occurrence. In addition to explaining why smaller and more disturbed habitats are unable to support resident insectivore populations, this bottom‐up mechanism may underlie the disproportionate sensitivity of insectivores to land‐use intensification.     

Arthropod community structure along a latitudinal gradient: Implications for future impacts of climate change

Abstract The structure of free‐living arthropod communities on the foliage of Acacia falcata was assessed along an extensive latitudinal gradient in eastern Australia. We hypothesized that abundance and biomass of arthropods within feeding groups would increase from temperate latitudes towards the tropics. We also hypothesized that the ratio of carnivores to herbivores would be consistent along the latitudinal gradient. Three sites at each of four latitudes, spanning 9° and 1150 km (Batemans Bay, Sydney, Grafton, Gympie in Australia), were sampled every season for 2 years, using pyrethrum knockdown. Abundance and biomass (based on dry weight) of arthropods within eight feeding groups were measured. The relative size of the feeding groups, and the ratio of carnivores to herbivores were then compared among latitudes and seasons. We found no consistent north to south (tropical to temperate) change in feeding group structure in terms of abundance. A weak latitudinal trend was evident for predator biomass, consisting of a reduction from north to south, but no significant trends in biomass for other feeding groups were found. Relative abundance and relative biomass of both carnivores and herbivores, as well as the ratio of carnivores to herbivores were consistent among latitudes. Finally, we compared a subset of these data to arthropod communities found on congeneric host species at individual sites along the latitudinal gradient. Overall, 68% of comparisons showed no significant differences in abundance or biomass within different feeding groups between host plants and among latitudes. We conclude that arthropod communities show consistencies among latitudes and between congeneric host species, in terms of feeding group and trophic structure. These results have implications for predicting the impacts of future climate change on arthropod communities.     

Cantharidin world on islands: Species diversity of canthariphilous arthropods in the Izu–Ogasawara Arc

Cantharidin is a defense chemical produced by only two beetle families, Meloidae and Oedemeridae. This compound also functions as an attractant for certain groups of arthropods (canthariphilous arthropods). Cantharidin‐producing beetles and canthariphilous arthropods build a cantharidin‐mediated community, called cantharidin world. In this study, to clarify the canthariphilous arthropod community formed on small islands, the arthropods were collected by cantharidin‐baited traps and compared among the mainland, peninsula and 11 small islands of the Izu–Ogasawara Arc, Japan. Control traps without cantharidin were also used to collect non‐canthariphilous arthropods. Cantharidin‐producing beetles were distributed across the study area, but the number of species was reduced on islands. We identified 10 species of five families as canthariphilous arthropods in this study area: two species of Anthicidae and Pyrochroidae (Coleoptera), four species of Ceratopogonidae (Diptera), three species of Formicidae (Hymenoptera) and one species of Podoctidae (Opiliones). The number of canthariphilous species was not correlated with island size (area) but was negatively correlated with the distance of island from the mainland. These tendencies were also seen in non‐canthariphilous fauna. The canthariphilous arthropods increased with the number of cantharidin‐producing beetle species, but the non‐canthariphilous fauna did not. Thus, the cantharidin world on islands seems to be affected not only by the geographic characteristics of islands, particularly the degree of isolation from the mainland, but also by the diversity of cantharidin‐producing members within it.     

A meta‐analysis of non‐consumptive predator effects in arthropods: the influence of organismal and environmental characteristics

Non‐consumptive effects (NCEs) – changes in prey behavior or physiology in response to predator threat – are common and can be as strong as consumptive effects. However, our knowledge of NCEs in arthropod systems is lacking. Factors related to study organism and environment have the potential to influence the occurrence and magnitude of NCEs in arthropod systems. While factors such as coevolutionary history of natural enemies and their prey, predator cue, predator or prey feeding mode, and refuge availability have been theoretically and empirically examined, no trends have been proposed for arthropods. We compiled 62 studies, yielding 128 predator–prey interactions, which explicitly examined NCEs in experiments where arthropods were identified to species, using a previously published database of papers from 1990 to 2005 and a new database of papers published from 2006 to 2015. Using these data, we conducted a meta‐analysis to explore the influence of organismal and environmental characteristics on the magnitude of predator NCEs. Our analysis addressed the following three questions. 1) Does predator–prey coevolution give rise to stronger NCEs than when predator and prey species did not coevolve? 2) What influence does habitat type and refuge availability have on NCEs? 3) How do predator characteristics (cue type, hunting mode and life stage) and prey characteristics (mobility, life stage, specialization, gregariousness and feeding mode) influence NCEs? We found that while NCEs were similar across most measured characteristics, NCEs on prey activity were significantly stronger when predator and prey shared an evolutionary history. Our results support growing evidence that NCEs have a negative effect on prey traits and that behavioral NCEs are stronger than physiological ones. Additional studies are needed to be confident in any emerging patterns, therefore we identify key gaps in the literature on NCEs in arthropod systems and discuss ideas for moving forward.     

Time, area and isolation: factors driving the diversification of Azorean arthropods

Aim R. J. Whittaker et al. recently proposed a ‘general dynamic model of oceanic island biogeography’ (GDM), providing a general explanation of island biodiversity patterns by relating fundamental biogeographical processes – speciation, immigration, extinction – to area (A) and time (T; maximum island geological age). We adapt their model, which predicts a positive relationship with area combined with a humped relationship to time (designated the ATT² model), to study the factors promoting diversification on the Azores for several arthropod groups. Location The Azorean archipelago (North Atlantic; 37–40° N, 25–31° W). Methods We use the number of single‐island endemics (SIEs) as a measure of diversification, to evaluate four different predictions for the variation in SIEs between different islands, derived from the GDM theory and our knowledge of the fauna and history of the Azores. We calculated the number of SIEs for seven out of the nine Azorean islands and six groups of species (all arthropods, beetles, cavernicolous and non‐cavernicolous species, and taxa with high and low dispersal abilities). Several variables accounting for island characteristics (area, geological age, habitat diversity and isolation) and generalized linear models were used to evaluate the reliability of each prediction. Results A linear and positive relationship between SIEs and an AT (area + time) model was the most parsimonious explanation for overall arthropod diversification. However, cavernicolous species showed the opposite pattern (more SIEs inhabiting the youngest islands). Also, isolation was an important predictor of diversification for all groups except for the species with high dispersal ability; while the former were negatively related to the distance from the main source of colonizing lineages (Santa Maria island in most cases), the latter were related to area. Dispersal ability was also a key factor affecting the diversification of most groups of species. Main conclusions In general, the diversification of Azorean arthropods is affected by age, area and isolation. However, different groups are affected by these factors in different ways, showing radically different patterns. Although the ATT² model fails to predict the diversification pattern of several groups, it provides a framework for integrating these deviations into a general theory. Further improvements of the GDM theory need to take into account the particular traits of each group and the role of isolation in shaping island diversity.     

Trophic cascades in tropical rainforests: Effects of vertebrate predator exclusion on arthropods and plants in Papua New Guinea

Insect herbivores have the potential to consume large amounts of plant tissue in tropical forests, but insectivorous vertebrates effectively control their abundances, indirectly increasing plant fitness accordingly. Despite several studies already sought understanding of the top-down effects on arthropod community structure and herbivory, such studies of trophic cascades in old tropics are underrepresented, and little attention was paid to top-down forces in various habitats. Therefore, we examine how flying insectivorous vertebrates (birds and bats) impact arthropods and, consequently, affect herbivore damage of leaves in forest habitats in Papua New Guinea. In a 3-month long predator exclosure experiment conducted at four study sites across varying elevation and successional stage, we found that vertebrate predators reduced arthropod density by ∼52%. In addition, vertebrate predators decreased the mean body size of arthropods by 26% in leaf chewers and 47% in non-herbivorous arthropods but had only a small effect on mesopredators and sap suckers. Overall, the exclusion of vertebrate predators resulted in a ~ 41% increase in leaf damage. Our results, across different types of tropical forests in Papua New Guinea, demonstrate that flying vertebrate insectivores have a crucial impact on plant biomass, create a selective pressure on larger and non-predatory prey individuals and they prey partition with mesopredators.