Fergnani Paula Nilda, Ruggiero Adriana
Laboratorio Ecotono, Centro Regional Universitario Bariloche-Universidad Nacional del Comahue, INIBIOMA-CONICET, San Carlos de Bariloche, Argentina.
PLoS One. 2017 Sep 5;12(9):e0184057. doi: 10.1371/journal.pone.0184057. eCollection 2017.
The latitudinal diversity gradient has been considered a consequence of a shift in the impact of abiotic and biotic factors that limit species distributions from the poles to the equator, thus influencing species richness variation. It has also been considered the outcome of evolutionary processes that vary over geographical space. We used six South American mammal groups to test the association of environmental and evolutionary factors and the ecological structuring of mammal assemblages with spatial variation in taxonomic richness (TR), at a spatial resolution of 110 km x 110 km, at tropical and extra-tropical latitudes. Based on attributes that represent what mammal species do in ecosystems, we estimated ecological diversity (ED) as a mean pairwise ecological distance between all co-occurring taxa. The mean pairwise phylogenetic distance between all co-occurring taxa (AvPD) was used as an estimation of phylogenetic diversity. Geographically Weighted Regression analyses performed separately for each mammal group identified tropical and extra-tropical high R2 areas where environmental and evolutionary factors strongly accounted for richness variation. Temperature was the most important predictor of TR in high R2 areas outside the tropics, as was AvPD within the tropics. The proportion of TR variation accounted for by environment (either independently or combined with AvPD) was higher in tropical areas of high richness and low ecological diversity than in tropical areas of high richness and high ecological diversity. In conclusion, we confirmed a shift in the impact of environmental factors, mainly temperature, that best account for mammal richness variation in extra-tropical regions, whereas phylogenetic diversity best accounts for richness variation within the tropics. Environment in combination with evolutionary history explained the coexistence of a high number of ecologically similar species within the tropics. Consideration of the influence of contemporary environmental variables and evolutionary history is crucial to understanding of the latitudinal diversity gradient.
纬度多样性梯度被认为是限制物种分布的非生物和生物因素的影响从极地向赤道转移的结果，从而影响物种丰富度的变化。它也被认为是在地理空间上变化的进化过程的结果。我们使用六个南美哺乳动物类群，在热带和温带纬度，以110公里×110公里的空间分辨率，测试环境和进化因素的关联以及哺乳动物群落的生态结构与分类丰富度（TR）空间变化之间的关系。基于代表哺乳动物物种在生态系统中行为的属性，我们将生态多样性（ED）估计为所有共存分类单元之间的平均成对生态距离。所有共存分类单元之间的平均成对系统发育距离（AvPD）被用作系统发育多样性的估计值。对每个哺乳动物类群分别进行的地理加权回归分析确定了热带和温带的高R2区域，在这些区域环境和进化因素强烈地解释了丰富度的变化。温度是热带以外高R2区域TR的最重要预测因子，而AvPD是热带地区的最重要预测因子。在高丰富度和低生态多样性的热带地区，由环境（单独或与AvPD结合）解释的TR变化比例高于高丰富度和高生态多样性的热带地区。总之，我们证实了环境因素（主要是温度）影响的转变最能解释温带地区哺乳动物丰富度的变化，而系统发育多样性最能解释热带地区丰富度的变化。环境与进化历史相结合解释了热带地区大量生态相似物种的共存。考虑当代环境变量和进化历史的影响对于理解纬度多样性梯度至关重要。
