We applied a multivariate analysis to investigate the roles of host and symbiont on the in situ physiological response of genus Madracis holobionts towards light. Across a large depth gradient (5-40 m) and for four Madracis species and three symbiont genotypes, we assessed several variables by measuring chlorophyll a fluorescence, photosynthetic pigment composition, or symbiont population descriptors. Most of the variation is explained by two major photobiological components: light-use efficiency and symbiont cell densities. Two other minor components emphasize photoprotective pathways and light-harvesting properties such as secondary pigments. Statistics highlight the role of irradiance on coral physiology and reveal mechanisms that are either genetically constrained, such as symbiont cell sizes, or environmentally dependent, such as photochemical efficiencies. Other parameters, such as cellular light-harvesting and photoprotective pigment concentrations, are regulated by host, symbiont, and environment. The interaction between host and environment stresses the role of host properties in adjusting the internal environment available for the endosymbionts. Different holobiont strategies, relating to symbiont cell density, vary in their physiological optimization of light-harvesting or photoprotective mechanisms and link to host-species distribution and dominance over the reef slope. Symbiont functional diversity appears to have a significant role but does not explain host vertical distribution patterns per se, highlighting the importance of species-specific morphological and physiological properties of the coral host.

Animals that rely on refuges for safety can theoretically increase their foraging area without simultaneously increasing predation risk and travel costs by using more refuges. The key prediction of this theory, a negative correlation between food abundance, home range size and the number of refuges used, has never been empirically tested. We determined how home range size and refuge use by the Central American agouti (Dasyprocta punctata) varied across a gradient of abundance of the agoutis' principal food source: seeds and fruits of the palm Astrocaryum standleyanum. We used both manual and automated radio telemetry to measure space use of 11 agoutis during 2 mo of the Astrocaryum fruiting season, and of another set of 10 agoutis during 6 mo in which the animals largely relied on cached Astrocaryum seeds. We found that agoutis living in areas of lower food density had larger home ranges, and that all individuals used multiple refuges. The number of refuges, however, was not correlated with home range size. Consequently, agoutis that had larger home ranges roamed farther from their refuges. These results suggest that agoutis increase their home range size in response to food scarcity at the cost of their safety.

BackgroundThe movement patterns of wild animals depend crucially on the spatial and temporal availability of resources in their habitat. To date, most attempts to model this relationship were forced to rely on simplified assumptions about the spatiotemporal distribution of food resources. Here we demonstrate how advances in statistics permit the combination of sparse ground sampling with remote sensing imagery to generate biological relevant, spatially and temporally explicit distributions of food resources. We illustrate our procedure by creating a detailed simulation model of fruit production patterns for Dipteryx oleifera, a keystone tree species, on Barro Colorado Island (BCI), Panama.Methodology and Principal FindingsAerial photographs providing GPS positions for large, canopy trees, the complete census of a 50-ha and 25-ha area, diameter at breast height data from haphazardly sampled trees and long-term phenology data from six trees were used to fit 1) a point process model of tree spatial distribution and 2) a generalized linear mixed-effect model of temporal variation of fruit production. The fitted parameters from these models are then used to create a stochastic simulation model which incorporates spatio-temporal variations of D. oleifera fruit availability on BCI.Conclusions and SignificanceWe present a framework that can provide a statistical characterization of the habitat that can be included in agent-based models of animal movements. When environmental heterogeneity cannot be exhaustively mapped, this approach can be a powerful alternative. The results of our model on the spatio-temporal variation in D. oleifera fruit availability will be used to understand behavioral and movement patterns of several species on BCI.