The interactions of behavioral patterns with landscape in influencing population structure

Executive summary: BSF Grant 2011384 PIs: Shirli Bar-David, Alan Templeton, Amos Bouskila From colonization to establishment: The interactions of behavioral patterns with landscape in influencing the population structure of the reintroduced wild ass This study aimed to explore the relationships between four levels of a population's structure – genetic, spatial, demographic and social - by formulating theoretical models specifically adjusted to colonizing populations in their establishment phase and by verifying the models with a case study of a reintroduced species, the Asiatic wild ass (Equus hemionus) population in the Negev desert. Here we briefly report the results of our study in the context of our original aims.

Develop a set of models that will form a theoretical framework: We developed two type of models: 1. A stochastic model to predict the allelic diversity in a newly founded expanding population, experiencing genetic drift and gene flow (Greenbaum et al. 2014, PlosOne) 2. A Species Distribution Model at three spatial scales, demonstrating the advantage of developing a high-resolution map to detect landscape features and habitat component important for the wild ass population (Nezer et al. 2016, Biodiversity and Conservation).

Measure empirically parameters that define genetic, spatial, demographic and social structure over time in an expanding population of a reintroduced species.

We detected a decline in the genetic diversity since reintroduction onset and a significant genetic structure within the wild ass population which had been developed over a short time frame and small area (Gueta et al. 2014, Renan 2014, PhD thesis, Speyer MSc thesis). We related this structure to the combined impact of landscape features, which affect species distribution and movement dynamics (Gueta et al. 2014; Davidson et al. 2013 Landscape Ecology; Giotto et al. 2016, PlosOne), behavioral patterns which affect site fidelity (Renan 2014, PhD thesis; Ziv MSc thesis; Giotto et al. 2016), social grouping patterns (Renan 2014, Renan et al. submitted, Ben-Nun, 2014 MSc thesis, Altman MSc thesis) and mating system (Renan, Greenbaum et al. 2015, Molecular Ecology) and demographic attributes such as the strong maternal heritability in RS (Greenbaum, Renan et al. in prep.). This genetic structure might diminish over time as the population will continue expanding its size and range. However, even a temporary genetic structuring has the potential of facilitating adaptive evolution and thereby affecting the population’s long term persistence.

Integrate the models with empirical data to fine-tune the models, validate them and create projections and predictions for future trajectories of the studied species.

We developed a stochastic model simulating the demographic growth and genetic dynamics of the Asiatic wild ass population following its reintroduction. In each simulation different proportions of males mated per generation. By comparing the genetic diversity as predicted by the model at different scenarios with the genetic data collected from the wild population, we were able to estimate a strong polygynous mating system in the reintroduced wild ass. Polygynous mating system in small population may decrease genetic diversity. Hence, long term monitoring is needed in order to study this dynamics in the endangered Asiatic wild ass and to apply the knowledge to management protocols. This research approach can be further used for other elusive/rare/small populations with implications to species conservation (Renan, Greenbaum et al. 2015 Molecular Ecology).