Abstract
The concept of generic diversity expresses the ‘diversification’ of species into genera in a community. Since niche overlap is assumed to be higher in congeneric species, competition should increase generic diversity. On the other hand, generic diversity might be lower in highly selective environments, where only species with similar adaptations can survive. We used the distribution of tenebrionid beetles in Central Italy to investigate how generic diversity varies with elevation from sea level to 2400 m altitude. Generic diversity of geophilous tenebrionids decreased sharply with elevation, whereas the generic diversity of xylophilous tenebrionids showed similarly high values across the gradient. These results suggest that geophilous species are more sensitive to variation in environmental factors, and that the advantages of close relationships (similar adaptations to harsh conditions) are greater than the possible drawbacks (competition). This is consistent with the fact that geophilous tenebrionids are mostly generalist detritivores, and hence weakly affected by competition for resources. By contrast, xylophilous species are more protected from harsh/selective conditions, but more limited by competition for microhabitats and food. Our results support the environmental filtering hypothesis for the species composition of tenebrionid beetles along an elevational gradient.
Highlights
Analyses were performed using R version 3.2.0 [68]. Both the total number of species and the total number of genera decreased with elevation according to a semilogarithmic function (Table 1, Figure 1a)
Species richness declined with elevation faster than the number of genera here too (ANCOVA: F1,44 = 46.68, p < 0.0000001)
In the case of the xylophilous species, both species richness and number of genera declined linearly with elevation (Table 1, Figure 1c). In this case species richness declined with elevation faster than the number of genera
Summary
The concept of generic diversity has been introduced to express the ‘diversification’ of species into genera [17], as the inverse of the probability that two species selected at random from a community belong to the same genus. Despite its simplicity, this measure has important ecological implications. As congeneric species are expected to be morphologically more similar than non-congeners, they should have more overlapping niches than species belonging to different
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