Biodiversity, Biogeography, & Conservation of North American Desert Fishes II: Faunal Assembly

Authors: Christopher Hoagstrom, Derek Houston, Norman Mercado-Silva

Year: 2018

Abstract

Desert-endemic fishes represent 53 clades from 14 families (based on a literature review). Many clades produced multiple endemic lineages (mean = 6 ± 8.2 SD). Estimates for timing of lineage origins are asynchronous (with some exceptions). Initiation of desert-endemism spanned a period of 23 million years, depending on lineage. Some clades diversified sequentially (e.g., Exoglossum; Moxostoma; Cyprinodon). Faunal dissimilarity among areas of endemism indicates that most lineage diversity arose independently, by area. Our conceptual model of faunal assembly illustrates a 2- or 3-step process in which an incipient-endemic lineage can diverge at any time, independent from other lineages, and an area of endemism may provide habitats in headwaters, alluvial streams & rivers, or springs. Step one: Founders colonize areas of endemism via passive (barrier formation) or active (dispersal) mechanisms. Step two: Persistence, possibly with adaptation, establishes residency. Areas with endemics become centers of survival. Step 3 (optional): Over time, areas accumulate diverse faunas through periodic colonization and/or in situ diversification. Areas accruing faunas become centers of accumulation. Areas with in situ diversification become centers of origin. Because of this process, each area of endemism has a unique assemblage with its own history. Hence, each area is a self-contained target for desert-fish conservation.