Tenorio, E. A. | bioRxiv Science

bioRxiv2020

The contribution of global mountains to the latitudinal diversity gradient

The latitudinal diversity gradient (LDG) is widely attributed to be the result of factors such as time, area, and energy. Although these factors explain most of the variation in lowlands, they fail in mountainous systems, which are biodiversity hotspots that may contribute meaningfully to the strength of the pattern following different evolutionary pathways. However, because lowlands cover the largest portion of the total land, they may have overshadowed the contribution of mountains to the LDG, but no study has addressed this issue in previous macroecological analyses. Here, we propose that the LDG shows a stronger trend in mountain ranges due to their high species turnover, in spite of covering less than one third of the Earth’s land. Using the geographical information for ∼22000 species of terrestrial vertebrates, we show that worldwide mountains harbor the 40% of the global diversity, and when taking into account the area effect, we quantified that mountains harbor close to double the species inhabiting lowlands per unit area. Moreover, when we evaluated the LDG after accounting for area size, we found that species richness increased faster towards the Equator and was better predicted by latitude in mountains than in lowlands. Our findings challenge previously well-supported hypotheses that predict that those regions with greater area, time and energy accumulate more species richness, since mountains are geologically younger, exhibit less energy, and cover smaller areas than lowlands. Hence, mountains represent a paradox, which invites to reevaluate hypotheses regarding macroecological and evolutionary processes driving species diversity gradients.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗

bioRxiv2020

100+ years of bird survey data reveal changes in functional fingerprints indexing ecosystem health of a tropical montane forest through time

Ecologically relevant traits of organisms inhabiting an ecosystem determine its functional fingerprint. Quantifying changes in the shape, volume and shifts in the position of functional fingerprints can provide information about the effects of diversity loss or gain through time, and is a promising means to monitor ecological integrity. This, however, is seldom possible owing to limitations in historical surveys and lack of data on organismal traits, particularly in diverse tropical regions. Using detailed bird surveys from four time periods across more than one century and morphological traits of 233 species, we quantified changes in the avian functional fingerprint of a tropical montane forest site in the Andes of Colombia. We found that 79% of the variation in functional space, regardless of time period, was described by three major axes summarizing body size, dispersal ability, and habitat breadth. Changes in species composition caused significant alterations of the functional fingerprint of the assemblage, with 35 – 60% reductions in functional richness and dispersion. Owing to species extirpations and to novel additions to the assemblage, functional space is currently smaller and at least 11% different to what it was a century ago, with fewer large-sized species, more good dispersers, and fewer habitat specialists. Extirpated species had high values of functional uniqueness and distinctiveness, resulting in large reductions of functional richness and dispersion after their loss, implying potentially important consequences for ecosystem functioning. Conservation efforts aimed at maintaining ecosystem function must move beyond maintaining species numbers to designing strategies for the maintenance of ecological function by identifying and conserving species with traits conferring high vulnerability.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗