Zoogeography of the Coleopterous Family Chauliognathidae

Abstract

ZOOGEOGRAPHIC philosophy to date has been based primarily on the distribution of vertebrate animals though it would seem that a study of invertebrate forms could also make an important contribution. Recognition of zoogeographic principles can be useful to the better understanding of other disciplines such as systematics and phylogeny. It has opened a fresh approach to my general study of Cantharoidea and has contributed to the delineation of a new family, Chauliognathidae (Miskimen, 1961), as well as suggesting other changes in cantharoid classification which will be treated in future papers. The fundamentals of invertebrate distribution are substantially the same as those affecting vertebrates, especially the poikilotherms (Darlington, 1948). The salient difference is timing. Almost all present-day insect families and many genera were well established at the close of the Cretaceous period while mammals and birds, on the distribution of which many prevailing zoogeographic conclusions are based, were only in very early stages of their evolution. Relatively few major evolutionary changes have occurred among insects since that time; the principal innovations are adaptations, usually at the generic level, correlated with new food sources made available by the Upper Cretaceous angiosperm expansion (Axelrod, 1952; Dorf, 1955). Geology and climatology of the past are particularly useful in the understanding of contemporary insect zoogeography because of a paucity of fossil evidence. Such indirect evidence, as well as inferences drawn from contemporary observations, assumes great importance when resolving puzzling geographic discontinuities and distributions. The beetle family, Chauliognathidae, is an especially good example. Chauliognathids are divided into two tribes, Chauliognathini and Ichthyurini, which are found today in rather restricted localities. The group is admirably suited to zoogeographic study because there are comparatively few species; these agree in generally limited spatial ranges, rather restricted habitats, and relative lack of association with man. Careful survey of their distribution adds materially to the appreciation of relationships between the various taxa, including species. In this paper, geology and climate will be discussed as a unit, followed by correlation with probable origins and dispersions to give a continuous picture of events leading to the contemporary distribution of Chauliognathidae.