Spatial Distribution and Dispersal Patterns of Central North American Freshwater Crayfish (Decapoda: Cambaridae) with Emphasis on Implications of Glacial Refugia

Spatial distributions of crayfish were evaluated in relation to glacial geography and possible modes of dispersal from refugia. Species dispersal patterns were a priori hypothesized and tested using principle components analysis (PCA). PCA factor loading plots were evaluated for hypothesized crayfish dispersal patterns. Cambarus laevis was limited to the unglaciated region, while Orconectes immunis, Orconectes virilis, and Procambarus gracilis may have dispersed from western glacial refugia in the upper Missouri drainage. Fallicambarus fodiens and Procambarus acutus dispersed from south of the glacial advance within the Mississippi embayment. Previous dispersal hypotheses for Orconectes propinquus recognized that northern refugia may have been from the Driftless Area in Wisconsin and Illinois and may have invaded more than one refuge since this species was common in unglaciated areas of southwestern Indiana. Orconectes indianensis center of abundance is in the unglaciated region. Disjunct populations likely dispersed into temporary glacial lakes that, when receded, left populations in previously glaciated areas. Cambarus polychromatus possibly dispersed from southern refugia, while Cambarus sp. A cf. diogenes dispersed from southern refugia not sympatric with C. polychromatus. The glacial refugia included western and southern areas of the glacial maximum; however, northern dispersal routes may be important with global climate change. 1. Introduction Changes in climate patterns during the Pleistocene (2.5 million: 11.7 thousand years ago), which brought on the advance of glacial ice through temperate environments, had substantial effects on species distributions [1, 2]. In glaciated areas, topographic diversity was reduced, drainage courses altered, and habitat changed greatly through deposits of large amounts of glacial till [1, 3]. These vicariant events of ice advance caused species to shift ranges south or to other areas of glacial refugia [2]. As ice sheets receded, many species that had been pushed from areas covered by ice, invaded or reinvaded, and many modern species distributions in glaciated regions reflect species dispersal after glacial events [1–6]. In central United States, areas of glacial refugia existed mainly south of the glacial maximum [1]. However, glacial refugia also existed in several isolated locations such as an area north of the glacial maximum known as the Driftless Area in southern Wisconsin and northwestern Illinois, in addition to portions of the upper Missouri river drainage and to the west [1, 3, 5]. Several authors [1,