Tropical dry forest trees and the relationship between local abundance and geographic range

Abstract

Aim To test the macroecological principle that a positive relationship exists between local abundance and geographic range size for tree communities in the tropical dry forest. Location Two tropical dry forest (TDF) regions on the Pacific coast of Mexico: one near Chamela, Jalisco; the other near Huatulco, Oaxaca. Methods We recorded species presence and relative abundance of trees and lianas from over 40 locales in each of the study regions using transects across an elevational gradient. We then compared the field data with occurrence data from national and online databases to examine how local patterns of abundance relate to putative geographic range areas and latitudinal breadth. Results We found no significant correlation between abundance and range size. Overall, many more locally abundant species had small ranges than large ones. We found that most species occupy the majority of the TDF range north of Colombia, and those species present in South America occupy the majority of that continent’s TDF range as well. This pattern was independent of local abundance. We also found no relationship between range size and local niche breadth as measured by elevation, or between local abundance and distance to the range centre. Main conclusions The macroecological tenet that posits a positive correlation between local abundance and geographic range size does not appear to hold for TDF trees. The finding that many locally abundant species had narrow ranges also suggests that dry forest endemics may be particularly well adapted to local conditions and make important contributions to community structure. We hypothesize that the absence of abundant species with large ranges is due to opposing environmental constraints that prevent a species from thriving everywhere.

Geographical Range and Local Abundance of Tree Species in China

“…We see no reasons to expect this bias: three plots we studied are in subtropical lowland forest, and their environmental conditions are similar to the entire subtropical area. Our results are consistent with the few studies on tree species we found: some reported no correlation between local abundance and range size [25], and others found either positive or negative, though weak relationships [50], [59].…”

“…There was no relation, consistent with the result from Williams et al . [25]. Evidently other factors accounting for species differences in abundance are much more important than the location of a range center.…”

Double Jeopardy and Global Extinction Risk in Corals and Reef Fishes

“…These endemics are often numerically dominant compared to most co-occurring pandemics [19,20], further suggesting that the lack of a positive abundance-range size relationship is a general phenomenon on coral reefs. Similarly, on land, some endemic species can be locally abundant [21], contributing in some cases to significant negative interspecific relationships between abundance and distribution [17].…”

Of niches and distributions: range size increases with niche breadth both globally and regionally but regional estimates poorly relate to global estimates

“…No -the authors classified species distributions into three categories (endemic, Mediterranean, widely distributed) Pither (2003) Tolerance Yes -the author measured area occupancy of species endemic to continental United States of America and Canada Williams et al (2010) Tolerance No -the authors excluded occurrence records outside the Western Hemisphere…”