Have old species reached most environmentally suitable areas? A case study with South American phyllostomid bats

Aim: We used ecological niche modelling to test different models explaining the lineage age-area relationship. We hypothesized that lineage age should influence the proportion of potential range unfilled by phyllostomid bat species. We made explicit predictions about possible relationships between the proportion of unfilled potential range and lineage age. Our goal was to analyse empirical data and fit the model that best describes our data. Location: South America. Methods: We modelled the ecological niche of 49 phyllostomid bat species using Maxent and Support Vector Machine (SVM). We calculated the proportion of unfilled potential range as the amount of area outside the current distribution divided by the current distribution (realized range size). Using a dated phylogeny, we regressed the proportion of unfilled potential range on lineage age. To compare our predictions we also regressed realized range size on lineage age. Results: Unfilled potential range was weakly associated with lineage age. This relationship was an inverse function of lineage age, explaining between 0 and 17% of the proportion of unfilled potential range. Furthermore, the relationship between realized range size and lineage age exhibited a logarithmic function, with lineage age explaining between 13 and 20% of the variation in realized range size. Main conclusions: Different regression models indicated that old phyllostomid species have smaller unfilled ranges than young species. That is, old species have filled most of the areas that are suitable for them. Furthermore, old species have larger realized ranges than young species. We thus refuted both the lineage age-area and taxon cycle models and lent support to the stasis post-expansion model. This suggests that bat species can reach most of their potential range rapidly after cladogenesis and such occupation remains more or less constant through time.