Biogeography of photoautotrophs in the high polar biome

The global latitudinal gradient in biodiversity weakens in the high polar biome and so an alternative explanation for distribution of Arctic and Antarctic photoautotrophs is required. Here we identify how temporal, microclimate and evolutionary drivers of biogeography are important, rather than the macroclimate features that drive plant diversity patterns elsewhere. High polar ecosystems are biologically unique, with a more central role for bryophytes, lichens and microbial photoautotrophs over that of vascular plants. Constraints on vascular plants arise mainly due to stature and ontogenetic barriers. Conversely non-vascular plant and microbial photoautotroph distribution is correlated with favourable microclimates and the capacity for poikilohydric dormancy. Contemporary distribution also depends on evolutionary history, with adaptive and dispersal traits as well as legacy influencing biogeography. We highlight the relevance of these findings to predicting future impacts on polar plant diversity and to the current status of plants in Arctic and Antarctic conservation policy frameworks

Advanced photogrammetry to assess lichen colonization in the hyper-arid Namib Desert

The hyper-arid central region of the Namib Desert is characterized by quartz desert pavement terrain that is devoid of vascular plant covers. In this extreme habitat the only discernible surface covers are epilithic lichens that colonize exposed surfaces of quartz rocks. These lichens are highly susceptible to disturbance and so field surveys have been limited due to concerns about disturbing this unusual desert feature. Here we present findings that illustrate how non-destructive surveys based upon advanced photogrammetry techniques can yield meaningful and novel scientific data on these lichens. We combined ‘structure from motion analysis,’ computer vision and GIS to create 3-dimensional point clouds from two-dimensional imagery. The data were robust in its application to estimating absolute lichen cover. An orange Stellarangia spp. assemblage had coverage of 22.8% of available substrate, whilst for a black Xanthoparmelia spp. assemblage coverage was markedly lower at 0.6% of available substrate. Hyperspectral signatures for both lichens were distinct in the near-infra red range indicating that Xanthoparmelia spp. was likely under relatively more moisture stress than Stellarangia spp. at the time of sampling, and we postulate that albedo effects may have contributed to this in the black lichen. Further transformation of the data revealed a colonization preference for west-facing quartz surfaces and this coincides with prevailing winds for marine fog that is the major source of moisture in this system. Furthermore, a three-dimensional ‘fly through’ of the lichen habitat was created to illustrate how the application of computer vision in microbiology has further potential as a research and education tool. We discuss how advanced photogrammetry could be applied in astrobiology using autonomous rovers to add quantitative ecological data for visible surface colonization on the surface of Mars.AdLR thanks the support of the grant CTM2015-64728-C2-2-R from the Spanish Ministry of Economy, Industry and Competitiveness.http://www.frontiersin.org/Microbiologyam2017Genetic

Patterns of Evolutionary Speed: In Search of a Causal Mechanism

The “integrated evolutionary speed hypothesis” proposes that the rate of genetic evolution influences all major biogeographical patterns of diversity including those associated with temperature, water availability, productivity, spatial heterogeneity and area. Consistent with this theory, rates of genetic evolution correspond with patterns of diversity and diversification. Here we review the mechanisms that have been proposed to explain these biogeographic patterns in rates of genetic evolution. Tests of several proposed mechanisms have produced equivocal results, whereas others such as those invoking annual metabolic activity, or a “Red Queen” effect, remain unexplored. However, rates of genetic evolution have been associated with both productivity mediated rates of germ cell division and active metabolic rates and these explanations therefore justify further empirical investigation

Appendix B. Summary assessments of productivity–plant species richness relationships not included in Mittelbach et al. (2001).

Summary assessments of productivity–plant species richness relationships not included in Mittelbach et al. (2001)

Appendix A. Summary assessments of productivity–plant species richness relationships included in Mittelbach et al. (2001).

Summary assessments of productivity–plant species richness relationships included in Mittelbach et al. (2001)

Appendix C. Citations for studies included in Appendices A and B.

Citations for studies included in Appendices A and B

Supplement 1. A summary of studies considered for inclusion in this study.

<h2>File List</h2><p> <a href="sources.txt">sources.txt</a> (md5: 20bfc4c09e0227443ec13f9afe345c70) </p><h2>Description</h2><p> sources.txt is tab-delimited file summarizing of all the studies considered for inclusion in the final analyses with justification for exclusion where necessary. Explanations for the columns are provided in the text file. For a full list of citations see <a href="appendix-A.htm">Appendix A</a>. </p