Regulation of body temperature poses significant problems for organisms that inhabit environments... more Regulation of body temperature poses significant problems for organisms that inhabit environments with extreme and seasonally fluctuating ambient temperatures. To help alleviate the energetic costs of autonomic responses, these organisms often thermoregulate through behavioral mechanisms. Among primates, lemurs in Madagascar experience uncharacteristically seasonal and unpredictable climates relative to other primate-rich regions. Malagasy primates are physiologically flexible, but different species use different mechanisms to influence their body temperatures. Lemur catta, the ring-tailed lemur, experiences particularly acute diurnal temperature fluctuations in its mostly open-canopy habitat in south and southwest Madagascar. Ring-tailed lemurs are also atypical among lemurs in that they appear to use both sun basking postures and huddling to maintain body temperature when ambient temperatures are cold. To our knowledge, however, no one has systematically tested whether these behaviors function in thermoregulation. We present evidence that ring-tailed lemurs use these postures as behavioral thermoregulation strategies, and that different environmental variables are associated with the use of each posture. Major predictors of sunning included ambient temperature, time of day, and season. Specifically, L. catta consistently assumed sunning postures early after daybreak when ambient temperatures were <13°C, and ceased sunning around 10:00a.m., after ambient temperatures approached 26°C. Sunning occurred more often during austral winter months. Huddling was associated with time of day, but not with ambient temperature or season. We conclude that L. catta tend to sun, rather than huddle, under cold weather conditions when sunning is possible. However, both sunning and huddling are important behavioral adaptations of L. catta that augment chemical thermoregulation and the absence of a dynamic, insulating pelage. Sunning and huddling help to account for the great ecological flexibility of the species, but these adaptations may be insufficient in the face of future changes in protective vegetation and temperature.
Several factors can influence primate distributions, including evolutionary history, interspecifi... more Several factors can influence primate distributions, including evolutionary history, interspecific competition, climate, and anthropogenic impacts. In Madagascar, several small spatial scale studies have shown that anthropogenic habitat modification affects the density and distribution of many lemur species. Ecological niche models can be used to examine broad-scale influences of anthropogenic impacts on primate distributions. In this study, we examine how climate and anthropogenic factors influence the distribution of 11 Eulemur species using ecological niche models. Specifically, we created one set of models only using rainfall and temperature variables. We then created a second set of models that combined these climate variables with three anthropogenic factors: distance to dense settlements, villages, and croplands. We used MaxEnt to generate all the models. We found that the addition of anthropogenic variables improved the climate models. Also, most Eulemur species exhibited reduced predicted geographic distributions once anthropogenic factors were added to the model. Distance to dense settlements was the most important anthropogenic factor in most cases. We suggest that including anthropogenic variables in ecological niche models is important for understanding primate distributions, especially in regions with significant human impacts. In addition, we identify several Eulemur species that were most Int J Primatol
Ruffed lemurs (genus Varecia) are often described as having a flexible social organization, such ... more Ruffed lemurs (genus Varecia) are often described as having a flexible social organization, such that both cohesive (low fission–fusion dynamics) and fluid (high fission–fusion dynamics) grouping patterns have been observed. In ruffed lemur communities with high fission–fusion dynamics, group members vary in their temporal and spatial dispersion throughout a communally defended territory. These patterns have been likened to those observed in several haplorrhine species that exhibit the most fluid types of fission–fusion social organization (e.g., Pan and Ateles). To substantiate and further refine these claims, we describe the fission–fusion dynamics of a black-and-white ruffed lemur (Varecia variegata) community at Mangevo, an undisturbed primary rainforest site in Ranomafana National Park, Madagascar. We collected instantaneous group scan samples from August 2007–December 2008 (4,044 observation hours) to study and characterize patterns of subgroup size, composition, cohesion, and social association. In 16 consecutive months, we never found all members of the community together. In fact, individuals spent nearly half of their time alone. Subgroups were small, cohesive, and typically of mixed-sex composition. Mixed-sex subgroups were significantly larger, less cohesive, and more common than either male-only or female-only subgroups. Subgroup dynamics were related to shifts in climate, phenology of preferred fruit species, and female reproductive state. On average, association indices were low. Males and females were equally gregarious; however, adult male–male associations were significantly weaker than any other association type. Results presented herein document striking differences in fission–fusion dynamics between black-and-white ruffed lemurs and haplorrhines, while also demonstrating many broad-scale similarities to haplorrhine taxa that possess the most fluid fission–fusion societies. Am. J. Primatol. 9999:XX-XX, 2015.
Several factors can influence primate distributions, including evolutionary history, interspecifi... more Several factors can influence primate distributions, including evolutionary history, interspecific competition, climate, and anthropogenic impacts. In Madagascar, several small spatial scale studies have shown that anthropogenic habitat modification affects the density and distribution of many lemur species. Ecological niche models can be used to examine broad-scale influences of anthropogenic impacts on primate distributions. In this study, we examine how climate and anthropogenic factors influence the distribution of 11 Eulemur species using ecological niche models. Specifically, we created one set of models only using rainfall and temperature variables. We then created a second set of models that combined these climate variables with three anthropogenic factors: distance to dense settlements, villages, and croplands. We used MaxEnt to generate all the models. We found that the addition of anthropogenic variables improved the climate models. Also, most Eulemur species exhibited reduced predicted geographic distributions once anthropogenic factors were added to the model. Distance to dense settlements was the most important anthropogenic factor in most cases. We suggest that including anthropogenic variables in ecological niche models is important for understanding primate distributions, especially in regions with significant human impacts. In addition, we identify several Eulemur species that were most Int J Primatol
At the proximate level, hormones are known to play a critical role in influencing the life histor... more At the proximate level, hormones are known to play a critical role in influencing the life history of mammals, including humans. The pituitary gland is directly responsible for producing several hormones, including those related to growth and reproduction. Although we have a basic understanding of how hormones affect life history characteristics, we still have little knowledge of this relationship in an evolutionary context. We used data from 129 mammal species representing 14 orders to investigate the relationship between pituitary gland size and life history variation. Because pituitary gland size should be related to hormone production and action, we predicted that species with relatively large pituitaries should be associated with fast life histories, especially increased fetal and postnatal growth rates. Phylogenetic analyses revealed that total pituitary size and the size of the anterior lobe of the pituitary significantly predicted a life history axis that was correlated with several traits including body mass, and fetal and postnatal growth rates. Additional models directly examining the association between relative pituitary size and growth rates produced concordant results. We also found that relative pituitary size variation across mammals was best explained by an Ornstein-Uhlenbeck model of evolution, suggesting an important role of stabilizing selection. Our results support the idea that the size of the pituitary is linked to life history variation through evolutionary time. This pattern is likely due to mediating hormone levels but additional work is needed. We suggest that future investigations incorporating endocrine gland size may be critical for understanding life history evolution.
We have little knowledge of how climatic variation (and by proxy, habitat variation) influences
t... more We have little knowledge of how climatic variation (and by proxy, habitat variation) influences the phylogenetic structure of tropical communities. Here, we quantified the phylogenetic structure of mammal communities in Africa to investigate how community structure varies with respect to climate and species richness variation across the continent. In addition, we investigated how phylogenetic patterns vary across carnivores, primates, and ungulates. We predicted that climate would differentially affect the structure of communities from different clades due to between-clade biological variation. We examined 203 communities using two metrics, the net relatedness (NRI) and nearest taxon (NTI) indices. We used simultaneous autoregressive models to predict community phylogenetic structure from climate variables and species richness. We found that most individual communities exhibited a phylogenetic structure consistent with a null model, but both climate and species richness significantly predicted variation in community phylogenetic metrics. Using NTI, species rich communities were composed of more distantly related taxa for all mammal communities, as well as for communities of carnivorans or ungulates. Temperature seasonality predicted the phylogenetic structure of mammal, carnivoran, and ungulate communities, and annual rainfall predicted primate community structure. Additional climate variables related to temperature and rainfall also predicted the phylogenetic structure of ungulate communities. We suggest that both past interspecific competition and habitat filtering have shaped variation in tropical mammal communities. The significant effect of climatic factors on community structure has important implications for the diversity of mammal communities given current models of future climate change.
Many factors contribute to the structure of primate communities, including historical processes, ... more Many factors contribute to the structure of primate communities, including historical processes, interspecific competition, and climate. Here, we quantify the phylogenetic structure of individual primate communities to evaluate these factors relative to a null model. Then, we examine the effects of species richness and local climate on variation in community phylogenetic structure. We analyze 71 haplorhine and 29 strepsirrhine communities in Africa and quantify their net relatedness (NRI) and nearest taxon (NTI) indices. Significantly low, i.e., phylogenetically even, NRI and NTI values are indicative of interspecific competition in the past, resulting in closely related species not being found in the same community. In contrast, significantly high, i.e., phylogenetically clustered, NRI and NTI values suggest that closely related species have similar ecological requirements, resulting in closely related species occupying the same community. In a second set of analyses, we used simultaneous autoregressive models to examine if species richness, rainfall, and temperature predict variation in community phylogenetic structure. Most individual communities exhibited phylogenetically random species assemblages. However, significantly structured haplorhine communities were even whereas strepsirrhine communities were clustered. Species richness significantly predicted variation in haplorhine phylogenetic structure, whereas abiotic factors significantly predicted variation in strepsirrhine phylogenetic structure. We suggest that past interspecific competition and habitat filtering have affected a relatively small proportion of African primate communities, but that past interspecific competition has more strongly influenced haplorhine communities whereas environmental conditions have more strongly influenced strepsirrhine communities. Our study illustrates the utility of phylogenetic metrics and spatially explicit models for understanding primate communities.
Primates have evolved a unique combination of visual specializations that differentiate them from... more Primates have evolved a unique combination of visual specializations that differentiate them from other mammals [Heesy, 2008, 2009; Kaas, 2013; Preuss, 2007; Ross & Martin, 2007]. Among these specializations is the presence of polymorphic or routine trichromatic color vision found in several primate lineages [Jacobs, 1993, 1994/1995; Jacobs, 2009; see Fig. S2].
Regulation of body temperature poses significant problems for organisms that inhabit environments... more Regulation of body temperature poses significant problems for organisms that inhabit environments with extreme and seasonally fluctuating ambient temperatures. To help alleviate the energetic costs of autonomic responses, these organisms often thermoregulate through behavioral mechanisms. Among primates, lemurs in Madagascar experience uncharacteristically seasonal and unpredictable climates relative to other primate-rich regions. Malagasy primates are physiologically flexible, but different species use different mechanisms to influence their body temperatures. Lemur catta, the ring-tailed lemur, experiences particularly acute diurnal temperature fluctuations in its mostly open-canopy habitat in south and southwest Madagascar. Ring-tailed lemurs are also atypical among lemurs in that they appear to use both sun basking postures and huddling to maintain body temperature when ambient temperatures are cold. To our knowledge, however, no one has systematically tested whether these behaviors function in thermoregulation. We present evidence that ring-tailed lemurs use these postures as behavioral thermoregulation strategies, and that different environmental variables are associated with the use of each posture. Major predictors of sunning included ambient temperature, time of day, and season. Specifically, L. catta consistently assumed sunning postures early after daybreak when ambient temperatures were <13°C, and ceased sunning around 10:00a.m., after ambient temperatures approached 26°C. Sunning occurred more often during austral winter months. Huddling was associated with time of day, but not with ambient temperature or season. We conclude that L. catta tend to sun, rather than huddle, under cold weather conditions when sunning is possible. However, both sunning and huddling are important behavioral adaptations of L. catta that augment chemical thermoregulation and the absence of a dynamic, insulating pelage. Sunning and huddling help to account for the great ecological flexibility of the species, but these adaptations may be insufficient in the face of future changes in protective vegetation and temperature.
Several factors can influence primate distributions, including evolutionary history, interspecifi... more Several factors can influence primate distributions, including evolutionary history, interspecific competition, climate, and anthropogenic impacts. In Madagascar, several small spatial scale studies have shown that anthropogenic habitat modification affects the density and distribution of many lemur species. Ecological niche models can be used to examine broad-scale influences of anthropogenic impacts on primate distributions. In this study, we examine how climate and anthropogenic factors influence the distribution of 11 Eulemur species using ecological niche models. Specifically, we created one set of models only using rainfall and temperature variables. We then created a second set of models that combined these climate variables with three anthropogenic factors: distance to dense settlements, villages, and croplands. We used MaxEnt to generate all the models. We found that the addition of anthropogenic variables improved the climate models. Also, most Eulemur species exhibited reduced predicted geographic distributions once anthropogenic factors were added to the model. Distance to dense settlements was the most important anthropogenic factor in most cases. We suggest that including anthropogenic variables in ecological niche models is important for understanding primate distributions, especially in regions with significant human impacts. In addition, we identify several Eulemur species that were most Int J Primatol
Ruffed lemurs (genus Varecia) are often described as having a flexible social organization, such ... more Ruffed lemurs (genus Varecia) are often described as having a flexible social organization, such that both cohesive (low fission–fusion dynamics) and fluid (high fission–fusion dynamics) grouping patterns have been observed. In ruffed lemur communities with high fission–fusion dynamics, group members vary in their temporal and spatial dispersion throughout a communally defended territory. These patterns have been likened to those observed in several haplorrhine species that exhibit the most fluid types of fission–fusion social organization (e.g., Pan and Ateles). To substantiate and further refine these claims, we describe the fission–fusion dynamics of a black-and-white ruffed lemur (Varecia variegata) community at Mangevo, an undisturbed primary rainforest site in Ranomafana National Park, Madagascar. We collected instantaneous group scan samples from August 2007–December 2008 (4,044 observation hours) to study and characterize patterns of subgroup size, composition, cohesion, and social association. In 16 consecutive months, we never found all members of the community together. In fact, individuals spent nearly half of their time alone. Subgroups were small, cohesive, and typically of mixed-sex composition. Mixed-sex subgroups were significantly larger, less cohesive, and more common than either male-only or female-only subgroups. Subgroup dynamics were related to shifts in climate, phenology of preferred fruit species, and female reproductive state. On average, association indices were low. Males and females were equally gregarious; however, adult male–male associations were significantly weaker than any other association type. Results presented herein document striking differences in fission–fusion dynamics between black-and-white ruffed lemurs and haplorrhines, while also demonstrating many broad-scale similarities to haplorrhine taxa that possess the most fluid fission–fusion societies. Am. J. Primatol. 9999:XX-XX, 2015.
Several factors can influence primate distributions, including evolutionary history, interspecifi... more Several factors can influence primate distributions, including evolutionary history, interspecific competition, climate, and anthropogenic impacts. In Madagascar, several small spatial scale studies have shown that anthropogenic habitat modification affects the density and distribution of many lemur species. Ecological niche models can be used to examine broad-scale influences of anthropogenic impacts on primate distributions. In this study, we examine how climate and anthropogenic factors influence the distribution of 11 Eulemur species using ecological niche models. Specifically, we created one set of models only using rainfall and temperature variables. We then created a second set of models that combined these climate variables with three anthropogenic factors: distance to dense settlements, villages, and croplands. We used MaxEnt to generate all the models. We found that the addition of anthropogenic variables improved the climate models. Also, most Eulemur species exhibited reduced predicted geographic distributions once anthropogenic factors were added to the model. Distance to dense settlements was the most important anthropogenic factor in most cases. We suggest that including anthropogenic variables in ecological niche models is important for understanding primate distributions, especially in regions with significant human impacts. In addition, we identify several Eulemur species that were most Int J Primatol
At the proximate level, hormones are known to play a critical role in influencing the life histor... more At the proximate level, hormones are known to play a critical role in influencing the life history of mammals, including humans. The pituitary gland is directly responsible for producing several hormones, including those related to growth and reproduction. Although we have a basic understanding of how hormones affect life history characteristics, we still have little knowledge of this relationship in an evolutionary context. We used data from 129 mammal species representing 14 orders to investigate the relationship between pituitary gland size and life history variation. Because pituitary gland size should be related to hormone production and action, we predicted that species with relatively large pituitaries should be associated with fast life histories, especially increased fetal and postnatal growth rates. Phylogenetic analyses revealed that total pituitary size and the size of the anterior lobe of the pituitary significantly predicted a life history axis that was correlated with several traits including body mass, and fetal and postnatal growth rates. Additional models directly examining the association between relative pituitary size and growth rates produced concordant results. We also found that relative pituitary size variation across mammals was best explained by an Ornstein-Uhlenbeck model of evolution, suggesting an important role of stabilizing selection. Our results support the idea that the size of the pituitary is linked to life history variation through evolutionary time. This pattern is likely due to mediating hormone levels but additional work is needed. We suggest that future investigations incorporating endocrine gland size may be critical for understanding life history evolution.
We have little knowledge of how climatic variation (and by proxy, habitat variation) influences
t... more We have little knowledge of how climatic variation (and by proxy, habitat variation) influences the phylogenetic structure of tropical communities. Here, we quantified the phylogenetic structure of mammal communities in Africa to investigate how community structure varies with respect to climate and species richness variation across the continent. In addition, we investigated how phylogenetic patterns vary across carnivores, primates, and ungulates. We predicted that climate would differentially affect the structure of communities from different clades due to between-clade biological variation. We examined 203 communities using two metrics, the net relatedness (NRI) and nearest taxon (NTI) indices. We used simultaneous autoregressive models to predict community phylogenetic structure from climate variables and species richness. We found that most individual communities exhibited a phylogenetic structure consistent with a null model, but both climate and species richness significantly predicted variation in community phylogenetic metrics. Using NTI, species rich communities were composed of more distantly related taxa for all mammal communities, as well as for communities of carnivorans or ungulates. Temperature seasonality predicted the phylogenetic structure of mammal, carnivoran, and ungulate communities, and annual rainfall predicted primate community structure. Additional climate variables related to temperature and rainfall also predicted the phylogenetic structure of ungulate communities. We suggest that both past interspecific competition and habitat filtering have shaped variation in tropical mammal communities. The significant effect of climatic factors on community structure has important implications for the diversity of mammal communities given current models of future climate change.
Many factors contribute to the structure of primate communities, including historical processes, ... more Many factors contribute to the structure of primate communities, including historical processes, interspecific competition, and climate. Here, we quantify the phylogenetic structure of individual primate communities to evaluate these factors relative to a null model. Then, we examine the effects of species richness and local climate on variation in community phylogenetic structure. We analyze 71 haplorhine and 29 strepsirrhine communities in Africa and quantify their net relatedness (NRI) and nearest taxon (NTI) indices. Significantly low, i.e., phylogenetically even, NRI and NTI values are indicative of interspecific competition in the past, resulting in closely related species not being found in the same community. In contrast, significantly high, i.e., phylogenetically clustered, NRI and NTI values suggest that closely related species have similar ecological requirements, resulting in closely related species occupying the same community. In a second set of analyses, we used simultaneous autoregressive models to examine if species richness, rainfall, and temperature predict variation in community phylogenetic structure. Most individual communities exhibited phylogenetically random species assemblages. However, significantly structured haplorhine communities were even whereas strepsirrhine communities were clustered. Species richness significantly predicted variation in haplorhine phylogenetic structure, whereas abiotic factors significantly predicted variation in strepsirrhine phylogenetic structure. We suggest that past interspecific competition and habitat filtering have affected a relatively small proportion of African primate communities, but that past interspecific competition has more strongly influenced haplorhine communities whereas environmental conditions have more strongly influenced strepsirrhine communities. Our study illustrates the utility of phylogenetic metrics and spatially explicit models for understanding primate communities.
Primates have evolved a unique combination of visual specializations that differentiate them from... more Primates have evolved a unique combination of visual specializations that differentiate them from other mammals [Heesy, 2008, 2009; Kaas, 2013; Preuss, 2007; Ross & Martin, 2007]. Among these specializations is the presence of polymorphic or routine trichromatic color vision found in several primate lineages [Jacobs, 1993, 1994/1995; Jacobs, 2009; see Fig. S2].
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Papers by Jason M. Kamilar
the phylogenetic structure of tropical communities. Here, we quantified the phylogenetic
structure of mammal communities in Africa to investigate how community structure
varies with respect to climate and species richness variation across the continent. In addition,
we investigated how phylogenetic patterns vary across carnivores, primates, and ungulates.
We predicted that climate would differentially affect the structure of communities
from different clades due to between-clade biological variation. We examined 203 communities
using two metrics, the net relatedness (NRI) and nearest taxon (NTI) indices. We
used simultaneous autoregressive models to predict community phylogenetic structure
from climate variables and species richness. We found that most individual communities exhibited
a phylogenetic structure consistent with a null model, but both climate and species
richness significantly predicted variation in community phylogenetic metrics. Using NTI,
species rich communities were composed of more distantly related taxa for all mammal
communities, as well as for communities of carnivorans or ungulates. Temperature seasonality
predicted the phylogenetic structure of mammal, carnivoran, and ungulate communities,
and annual rainfall predicted primate community structure. Additional climate variables
related to temperature and rainfall also predicted the phylogenetic structure of ungulate
communities. We suggest that both past interspecific competition and habitat filtering have
shaped variation in tropical mammal communities. The significant effect of climatic factors
on community structure has important implications for the diversity of mammal communities
given current models of future climate change.
the phylogenetic structure of tropical communities. Here, we quantified the phylogenetic
structure of mammal communities in Africa to investigate how community structure
varies with respect to climate and species richness variation across the continent. In addition,
we investigated how phylogenetic patterns vary across carnivores, primates, and ungulates.
We predicted that climate would differentially affect the structure of communities
from different clades due to between-clade biological variation. We examined 203 communities
using two metrics, the net relatedness (NRI) and nearest taxon (NTI) indices. We
used simultaneous autoregressive models to predict community phylogenetic structure
from climate variables and species richness. We found that most individual communities exhibited
a phylogenetic structure consistent with a null model, but both climate and species
richness significantly predicted variation in community phylogenetic metrics. Using NTI,
species rich communities were composed of more distantly related taxa for all mammal
communities, as well as for communities of carnivorans or ungulates. Temperature seasonality
predicted the phylogenetic structure of mammal, carnivoran, and ungulate communities,
and annual rainfall predicted primate community structure. Additional climate variables
related to temperature and rainfall also predicted the phylogenetic structure of ungulate
communities. We suggest that both past interspecific competition and habitat filtering have
shaped variation in tropical mammal communities. The significant effect of climatic factors
on community structure has important implications for the diversity of mammal communities
given current models of future climate change.