Community Assembly and the Functioning of Ecosystems in Open Systems

Postdoc Research with Morgan Ernest and Mathew Leibold

“Community and ecosystem ecology often focuses on a single community, but communities are often linked because organisms disperse between them.  If dispersal changes the species composition and distribution of functional traits in a community it can alter the functioning of the ecosystem.  We are examining many different ecosystems and taxa to determine the importance of dispersal for determining how the composition of communities responds to environmental change and how this can have cascading impacts on ecosystem function.”

Associated presentations and publications:

  1. Bannar-Martin, K.H., Leibold, M., Kremer, C. & Ernest, M. (2015). The sCafe workshop at sDiv: Community assembly and the functioning of ecosystems in open systems. iDiv Annual Conference 2015, Leipzig, Germany. December 2015. (Podium presentation)

Scale and Process: Primate and Non-Primate Mammal Community Composition and Diversity in Madagascar

Ph.D. Research

The study of community assembly, or the processes that shape the occurrence of species in an ecological community, is a fundamental area of inquiry in ecology. Patterns in community composition and diversity are attributed to the combined operation of deterministic (e.g., environmental sorting), stochastic (e.g., dispersal limitation), and biogeographic (e.g., dispersal barriers) processes. Environmental sorting results in communities composed of species that are ecologically adapted to their environment. Dispersal limitation results in communities shaped by the dispersal distance between sites. Biogeographic dispersal barriers prevent species dispersal between sites, and community membership is dependent upon site isolation. Community assembly is also dependent upon diversity type (taxonomic, functional, or phylogenetic) and spatial scale.

I investigated the processes shaping the diversity of primate and nonvolant mammal communities using taxonomic, functional and phylogenetic diversity measures and a spatially explicit modelling approach. I described mammal diversity patterns at ecoregional, regional, and inter-regional scales within and across Madagascar and Australia. I tested the relationship of mammal community diversity to environmental, spatial, and biogeographic variables, indicating deterministic, stochastic, and biogeographic processes, in Madagascar and Australia. First, I found that arboreal mammal communities in Madagascar were more dispersal-limited than terrestrial mammal communities. Second, a combination of environmental sorting and dispersal limitation best explained primate taxonomic and functional diversity. Third, I tested for convergent diversity and assembly patterns in Madagascar and Australia, due to similar biogeographic and evolutionary histories, and found non-convergent patterns. Overall, biogeographic dispersal barriers were weak predictors of mammal diversity in Madagascar and Australia. Phylogenetic and functional diversity measures were weakly correlated, and phylogenetic diversity provided models with weak explanatory power. Environmental and spatial variables indicating the combined operation of environmental sorting and dispersal limitation variably shaped the taxonomic and functional diversity of mammal communities in Madagascar and Australia. Mammal community diversity was regionally specific, shaped by the unique historical and landscape components of each region, including ecoregional effects and the extinction of sympatric species. Macroscale studies of diversity should carefully investigate the influence of spatial scale and regional factors that can result in varied assembly patterns and unique ecological communities, such as those present for the nonvolant mammals of Madagascar and Australia.

Associated presentations and publications:

  1. Bannar-Martin, K.H. 2014. Primate and non-primate mammal community assembly: the influence of biogeographic barriers and spatial scale. International Journal of Primatology. 35(6): 1122-1142.  DOI: 10.1007/s10764-014-9792-2 [Erratum: 35(6):1143] (Invited)
  2. Bannar-Martin, K.H. 2014. Different diversity measures tell different primate community assembly stories. American Journal of Physical Anthropology. 153(S58): 72. (Student Presentation Honourable Mention)
  3. Bannar-Martin, K.H. 2013. Using spatial structural equation modeling as a novel approach to understanding primate community composition and diversity. American Journal of Physical Anthropology. 150(S56): 73-74. (Invited)
  4. Bannar-Martin, K.H. “Scale and Process: Primate and Non-Primate Mammal Community Composition and Diversity in Madagascar.” AAUW Austin Branch May meeting, Austin, TX, May, 2013. (Guest Lecture, Invited)

The influence of edge effects on lemur feeding ecology and spatial ecology.

M.Sc. Research

My Master’s thesis was on the effects of interior and exterior forest edges on Milne-Edward’s Sifakas’ (Propithecus edwardsi) spatial and feeding ecology. At the time, few edge effect studies on primates were done, and most were censuses that did not describe altered ecology in the study groups. In addition, interior versus exterior edge effects had not been compared. My approach was to document forest floral characteristics from the edge into the core forest to measure edge boundaries, and to document animals’ diet, behaviour and location with respect to the internal or external forest edge.

Edge effects, measured as changes in vegetation structure and plant species richness from the edge into the forest core, pose potential constraints on primate ranging, dispersal and behaviour. Edges, natural or anthropogenic, are important landscape features in impacted areas, as edge effects are often magnified by disturbance and change habitat suitability. Edges are dynamic zones characterized by the penetration, to varying depths and intensities, of abiotic conditions (e.g. wind, temperature, humidity, solar radiation) from the matrix into the forest interior. This penetration of abiotic factors results in changes in vegetation structure, microclimate, and food resources along edges. Primates can mediate edge effects by adjusting their ranging behaviour with respect to both edge proximity and edge type. An edge’s influence on animal ecology results in one of three possible edge responses: positive, negative or neutral. The variance in edge responses of local fauna and flora is important to both animal ecology and predicting the potential danger of forest edges being ‘ecological traps,’ in which organisms occupy edge habitats that cannot support their long-term survival due to increased predation pressure. I described the differences in feeding ecology and habitat use relative to forest edges in Propithecus edwardsi groups inhabiting two sites in Ranomafana National Park, Madagascar. Two edge types were distinguished: internal edges, located within continuous forest (a rice paddy), and external edges, located on forest boundaries (Namorona River). Behavioural and location data were collected May to September 2008, and used with GIS to determine lemur distribution and behaviour with respect to edge proximity and type. The position and type of edge was found to have a lasting impact on the floral composition of the forest and distribution of food resources. The highest proportion of range use and feeding events in P. edwardsi occurred within 250m of the edge: a positive edge response. The strength of the edge response differed between the two sites, with a stronger response in the external edge site. P. edwardsi in the external edge site also had a smaller home range, larger core range, and higher density. P. edwardsi show a positive edge response, however the strength of edge response appeared to vary with edge type. Edges are complicated habitat features that reflect microhabitats with multidimensional characteristics (e.g. intensity, depth, height, location, age, etc). Edge effects can have long-term impacts on primate behaviour, and consequently their role in primate ecology is fundamental to the conservation of primate populations.

Associated presentations and publications:

  1. Bannar-Martin, K.H. and S.M. Lehman. 2010. Interior versus exterior edges: Their effect on home range, spatial ecology and feeding ecology of Milne-Edwards’ Sifakas (Propithecus edwardsi) in Ranomafana National Park, Madagascar. American Journal of Physical Anthropology. 141(S50): 60-61.
  2. Bannar-Martin, K.H. “Interior versus exterior edges: their effect on home range, spatial ecology and feeding ecology of Milne-Edwards’ Sifakas in Ranomafana, Madagascar.” Texas Association of Biological Anthropologists Annual Meeting, Austin, TX. November 2009. (Podium Presentation, Best Student Presentation Award)

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