I am a Research Scientist and the Program Coordinator for the Duke Lemur Center SAVA Conservation program at Duke University. Our goal is to enhance biodiversity conservation in Madagascar through partnerships with local stakeholders, including the Madagascar National Parks, private reserves, and other entities.
Our focus is improving human livelihoods and creating benefits from ecosystem conservation. We do this through a number of unique programs:
1) environmental education, especially training local teachers (over 2600 so far) to incorporate environmental issues into their daily curriculum, as well as visits to natural reserves with school groups
2) reforestation and restoration, partnering with local communities to plant trees in their land for multiple purposes, including restoring natural habitats and agroforestry to mix cash-crops, timber trees, and native trees
3) regenerative agriculture training, especially diversifying crops and permaculture
4) fuel-efficiency, especially fuel-efficient cook stoves that use less firewood or charcoal than traditional methods
5) alternative food sources, including fish farming and the potential for insects as an alternative protein source to wild-caught animals
6) women's reproductive health, working with Marie Stopes International to improve women's health and the availability of contraceptives to those that want them,
7) supporting the Madagascar National Parks service for conservation monitoring and infrastructure development
And many more!
Stay tuned for updates on our work, which I plan to post in my blog and through social media!
In my previous postdoctoral project, I worked with Dr. Charles Nunn in the Evolutionary Anthropology department and Duke Global Health Institute. We continue to work on combining my interests in community ecology with Dr. Nunn's specialty in infectious disease to explore how parasite species richness is related to behavioral and environmental factors across all primates and small mammals of Madagascar. Our work is leveraging Dr. Nunn's comprehensive Global Mammal Parasite Database, which compiles data on parasite species occurrence and prevalence for primates, carnivores, and hooved animals. We will explore novel questions in the co-evolution of primates and parasites to understand the socio-ecological factors that place species at risk of diseases.
In addition, we are investigating patterns of disease transmission in small mammals of Madagascar, with on-going data collection in northeastern Madagascar. We have collected rodents, tenrecs, and shrews from six habitat types to screen for parasites. Thus far, we've collected data from over 600 animals and discovered at least five different species of nematode worms, collected over 4,000 ticks, fleas, and mites, and screened over 500 animals for the water-borne pathogen Leptospira, which is carried by small mammals and can be transmitted to people who drink the water. We are supported by Duke University through the Bass Connections program to bring Duke undergrad and graduate students to Madagascar and team up with Malagasy students and villagers to continue exploring the role of habitat and community ecology on disease transmission. Dr. Nunn also received funding from the NIH to expand the project, and I continue to facilitate the team as the DLC-SAVA program coordinator in Madagascar.
I am interested in the diversity of life and what causes variation in diversity across different groups of organisms (lineages), across space, and through time. I am fascinated by how dramatically diversity can change from one habitat to another, or from one taxonomic group to another. One classic example is the pattern of increasing diversity towards the equator (Rolland et al. 2014). But what explains variation in diversity? Age is an important factor; on first principles, one can assume that older lineages should have more species than younger linages because older lineages have had more time for speciation to occur. This pattern does not always hold true, however, and other hypotheses are necessary to explain variation in diversity (Rabosky et al. 2012). Different rates of diversification (speciation rate – extinction rate) affect diversity; assuming two groups of organisms are the same age, the one with higher diversification will have more species. But then what drives variation in diversification rates?
Research on diversification rates is clarifying the roles of traits and environment on diversification, both using the fossil record and using reconstructed evolutionary trees of living species. To date, several characteristics of species have been shown to affect diversification rates, including higher speciation and lower extinction in the tropics than in temperate regions (Rolland et al. 2014), higher diversification in terrestrial than aquatic vertebrates (Wiens 2015a; Wiens 2015b), higher diversification of herbivorous and winged insects than non-herbivorous and non-winged insects (Wiens et al. 2015), and higher diversification in herbivorous mammals than in omnivorous or carnivorous mammals (Price et al. 2012). Further, diversification rate shifts in the past can be correlated with paleoenvironments (Condamine et al. 2013; Quental and Marshall 2013), changes in traits like body size (Rabosky et al. 2013), and past ecological opportunity (Rabosky 2009).
In primates, species richness varies across continents and among lineages. Species richness has also varied greatly over time, with pulses of diversification punctuated by extinction events that have wiped out previously dominant lineages. Some of the patterns in diversification observed in the evolutionary tree of living primates suggest that diversification increased around the Miocene (~20 million years ago, Ma) and Miocene/Pliocene (~7Ma), but analyses with trees from living species do not reflect the known extinction events evident from the fossil record (Springer et al. 2012). I have found that the diversification of lemurs from Madagascar and lorisiforms from Africa and Asia differed in that lemurs had a higher speciation and extinction rate than lorisiforms, as predicted by the ecological theory of adaptive radiation.
These patterns suggest that primate lineages have undergone different evolutionary trajectories across space and through time. My research focuses on how and why. Check out some of my recent papers in the Publications section to see more.
For my PhD, I focused on the lemurs from Madagascar. This endemic group of primates seems to have dispersed from Africa or Asia to Madagascar ~50-60 Ma, and once they arrived, they evolved in isolation, with no competition from other primate groups that arose later on the mainland. Further, Madagascar is an ecologically diverse island, with rainforest, dry forests and deserts that may have influenced speciation and extinction rates. Lastly, predators and potential competitors arrived much later than lemurs, which may have triggered renewed diversification in line with the Red Queen hypothesis (Van Valen 1973). I sought to infer a near-complete phylogeny of lemurs, including the extinct subfossil lemurs, and place them in the greater context of the primate evolutionary tree with ancient fossils. I then compared the diversification dynamics of lemurs and their sister clade, the lorisiforms, to test the predictions of the ecological theory of adaptive radiation with lemurs as an empirical case. I inferred the biogeographic history of lemurs on Madagascar to test alternate hypotheses of ecological adaptation and geographic barriers for the in situ diversification of lemurs. Finally, I tested hypotheses of local community assembly with data on species abundances in different habitats from field surveys in southeast Madagascar.
The first step in this study was to infer the phylogeny of lemurs. Many studies have sought to clarify the evolutionary relationships among lemur species, but resolving the relationships among lemur families has proven difficult with molecular data alone (Horvath et al. 2008; Horvath and Willard 2007). I took a total evidence approach, combining molecular and morphological data from living and extinct lemurs, lorises, and a suite of primate outgroups including living and extinct monkeys, as well as the earliest fossil primates from 50-60 Ma. The resulting phylogenies had strong support for the relationships among lemurs, and provide a time calibrated tree that changes our interpretation of the tempo and mode of lemur evolution (Herrera and Dávalos 2016).
Next I compared the diversification dynamics of lemurs to the African and Asian lorisiforms to test the predictions of the ecological theory of adaptive radiation. I found that lemurs had a higher speciation and extinction rate than lorisiforms, and for both clades diversification rates did not decline through time, as would be predicted if lemur diversity had reached a maximum. In contrast, lemur diversification rates increased through time. In other ways, lemurs do fit the predictions of an adaptive radiation. For example, body mass evolutionary rate was highest early in lemur evolution and declined towards the present, which fits the prediction of an ‘early burst’ of phenotypic evolution followed by a slowdown in evolutionary rate as niches were filled. Further, body mass evolved according to an adaptive model in which species in different adaptive zones (based on activity pattern and diet) had different optimal phenotypes. The results suggest that some processes, potentially ecological interactions with predators or competitors as well as biogeographic evolution, have resulted in increasing diversification rates through time for lemurs while lemur phenotypes evolved according to a niche-filling model (Herrera 2017).
The remarkable species diversity of lemurs is paralleled by their ecological diversity – many species are endemic to either rainforests, dry forests, or spiny deserts. This led early researchers to hypothesize ecological barriers to dispersal that may have resulted in the current distribution of lemurs. Other studies have suggested that lemur distributions are the result of abiotic barriers, such as rivers or mountains, and still others hypothesize that recent (Pleistocene, ~ 2 Ma) climate change restricted some species to isolated forest refugia where they speciated, while other species that tolerate high elevations used montane dispersal corridors to maintain wide distributions. I used a likelihood-based biogeographic inference framework in which each hypothesis was parameterized by different dispersal probabilities among regions and changes in dispersal probabilities through time (BioGeoBEARS, Matzke 2014). I found the strongest support for a model in which the geographic distance among regions is the best predictor of the dispersal probability; adjacent regions have a higher dispersal probability than non-adjacent regions. Further, there is little support for changes in dispersal probability through time.
To compliment the biogeographic hypotheses tested above, I also quantified lemur biogeography in terms of the phylogenetic and functional diversity of 100 lemur communities across Madagascar (Herrera 2017, Int. J. Primatol.). I related the phylogenetic and functional diversity to environmental variables and tested if changes in diversity across space are related to geographic barriers or environmental variation. I found that the highest diversity occurs in eastern rainforests, and that communities consist of species that are more distantly related and more functionally dissimilar than predicted by chance alone. These results support the role of competition as an important process driving community assembly. The change in diversity across the island is best explained by the change in plant productivity; the greatest differences in diversity among pairs of sites also have the greatest differences in plant productivity. These results further support the roles of biotic interactions in shaping lemur diversity.
I expanded on the importance of this evolutionary history for the conservation value of the protected areas, and could use the evolutionary diversity and rate of habitat loss to rank protected areas (Herrera 2017).
Lastly, I tested hypotheses of local community assembly for five sites in southeast Madagascar using field surveys to quantify lemur species abundance as well as botanical composition in relation to elevation and anthropogenic habitat degradation. I found that the species that co-occurred were distantly related and had significantly different abundances. In habitats with high relative abundance of food trees, however, species tend to be more closely related than expected by chance, suggesting that a few closely related species dominate habitats with high food abundance. Elevation also had a significant effect on the phylogenetic structure of communities; at low elevations species were more closely related than expected by chance and at high elevations species were more distantly related than expected. Lastly, trait diversity was positively related to phylogenetic diversity, further supporting the role of competition in explaining community assembly (Herrera 2016).
Previous postdoctoral fellowship:
For my postdoctoral fellowship at the AMNH, I expanded from lemurs to all primates – how has diversification varied with biogeography, time, paleoenvironments and community composition for all primates across the globe and in deep time?
I first quantified variation in speciation and extinction rates through time and across clades using comprehensive data on the timing of almost 600 fossils. I tested if the speciation and extinction rates based on fossils were different from those rates calculated based on the phylogeny of living species. I found that the rates are significantly different, with rates from the phylogeny 10 times lower than the rates from fossils. Further, the calculations based on the phylogeny yield extinction rates near zero, while the fossils provide a clear record of high extinction rates. The results of this study were published in the the journal Evolution.
The next step was to create a near-complete phylogeny for all primates including extinct and extant taxa. I gathered published and new morphological data for living and fossil primates from museum collections. I use an online database for morphological data called MorphoBank that allows explicit documentation of the anatomical features used to estimate the evolutionary relationships between living and extinct species. I have combined these data with molecular data available for almost all living species and several subfossil species. I have been using a total evidence dating approach that parameterizes the inferred speciation and extinction rates of the tree based on the fossils actually in the tree. The preliminary results are very exciting, stay tuned!
I have also been investigating the biogeography and community ecology in Madagascar by expanding from lemurs to include more taxonomic groups, including bats, carnivores, tenrecs, and rodents. I have been collaborating with specialists at the AMNH Center for Biodiversity and Conservation to test if the patterns observed for lemurs hold for other groups as well.
With my postdoc advisor Dr. Nancy Simmons, I was also privileged to collaborate on her long-term project on bat diversity in Belize. Together we investigated how bat diversity is affected by forest fragmentation, learning that functional traits related to roost preference were key factors in determining which species could persist in fragmented landscapes.
I received my Bachelors in Arts degree in 2009 from the University of Miami (FL) in Anthropology. I earned my Master of Arts degree in 2011 from Stony Brook University (NY) in Anthropology and received my Ph.D. in 2015 from the Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University (NY).
Condamine FL, Rolland J, and Morlon H. 2013. Macroevolutionary perspectives to environmental change. Ecol Lett 16(s1):72-85.
Herrera JP. in prep. Diversification dynamics of lemurs from Madagascar: a test of the ecological theory of adaptive radiation in an island-endemic primate lineage. Proc R Soc Lond, Ser B: Biol Sci.
Herrera JP. submitted. Interactions between plants and primates shape community diversity in a rainforest in Madagascar. J Anim Ecol.
Herrera JP, and Dávalos L. accepted. Phylogeny and divergence times of lemurs inferred with recent and ancient fossils in the tree. Syst Biol.
Horvath JE, Weisrock DW, Embry SL, Fiorentino I, Balhoff JP, Kappeler P, Wray GA, Willard HF, and Yoder AD. 2008. Development and application of a phylogenomic toolkit: Resolving the evolutionary history of Madagascar’s lemurs. Genome Res 18(3):489-499.
Horvath JE, and Willard HF. 2007. Primate comparative genomics: lemur biology and evolution. Trends Genet 23(4):173-182.
Jetz, W., G. Thomas, J. Joy, K. Hartmann and A. Mooers (2012). "The global diversity of birds in space and time." Nature 491(7424): 444-448.
Matzke NJ. 2014. Model selection in historical biogeography reveals that founder-event speciation is a crucial process in island clades. Syst Biol 63(6):951-970.
Price SA, Hopkins SS, Smith KK, and Roth VL. 2012. Tempo of trophic evolution and its impact on mammalian diversification. Proceedings of the National Academy of Sciences 109(18):7008-7012.
Quental TB, and Marshall CR. 2013. How the Red Queen drives terrestrial mammals to extinction. Science 341(6143):290-292.
Rabosky DL. 2009. Ecological limits and diversification rate: alternative paradigms to explain the variation in species richness among clades and regions. Ecol Lett 12(8):735-743.
Rabosky DL, Santini F, Eastman J, Smith SA, Sidlauskas B, Chang J, and Alfaro ME. 2013. Rates of speciation and morphological evolution are correlated across the largest vertebrate radiation. Nature communications 4.
Rabosky DL, Slater GJ, and Alfaro ME. 2012. Clade age and species richness are decoupled across the eukaryotic tree of life. PLoS Biol 10(8):e1001381.
Rolland J, Condamine FL, Jiguet F, and Morlon H. 2014. Faster speciation and reduced extinction in the tropics contribute to the mammalian latitudinal diversity gradient. PLoS Biol 12(1):e1001775.
Springer MS, Meredith RW, Gatesy J, Emerling CA, Park J, Rabosky DL, Stadler T, Steiner C, Ryder OA, and Janečka JE. 2012. Macroevolutionary dynamics and historical biogeography of primate diversification inferred from a species supermatrix. PLoS ONE 7(11):e49521.
Van Valen LM. 1973. A new evolutionary law. Evolutionary Theory 1:1-30.
Wiens JJ. 2015a. Explaining large-scale patterns of vertebrate diversity. Biol Lett 11(7):20150506.
Wiens JJ. 2015b. Faster diversification on land than sea helps explain global biodiversity patterns among habitats and animal phyla. Ecol Lett.
Wiens JJ, Lapoint RT, and Whiteman NK. 2015. Herbivory increases diversification across insect clades. Nature Communications 6.