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A phylogenetic analysis for the North American Schizocosa species was undertaken by scoring 49 morphological characters for 31 taxa representing all of the Nearctic species of Schizocosa plus individuals that are hybrids between S. ocreata and S. rovneri. Rabidosa rabida, Allocosa georgicola and Gladicosa pulchra were used as outgroups. Three clades are recognized: a large clade from eastern North America (Clade A) within which is nested the S. ocreata clade; Clade B, which includes the widespread S. avida and the western 5'. mccooki, and a smaller, third clade, Clade C. Sexual ornamentation occurs on the first legs of mature males of several species within the Schizocosa and takes the form of pigmentation and or bristles primarily on the tibia of leg I; there is at least one species with bristles in each of the three main clades. Mapping the occurrence of male ornamentation on the preferred phylogeny suggests that ornamentation evolved 5 or 6 separate times and was subsequently lost 2 or 3 times. The ornamentation is concentrated in the S. ocreata clade, a clade defined by a finger like projection on the paleal process of the male pedipalp. Courtship behavior is known for 20 of the 3 1 taxa. All species studied utilize chemical communication and seismic signals for communication; some species also have distinct visual signals. Seismic signals are produced by palpal drumming (as is seen in several species within Clade B), or by stridulation (seen in Clade A). Visual signals consisting of movements of the first pair of legs are common in species that are distinctly ornamented. This study provides the first phylogenetic study of a North American genus of wolf spider and provides morphometric comparisons of the North American species in Schizocosa.

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The courtship behaviors of two morphologically similar spider species, Schizocosa ocreata and S. rovneri, are distinctive and prevent interbreeding. We used “forced” copulation between these species to investigate the mode of inheritance of the courtship behavior and to determine whether postmating isolating mechanisms exist. F1 hybrids proved to be behaviorally sterile, but they were capable of producing viable offspring when forced to interbreed. Analysis of the courtship behaviors of F1, F2, and backcross progeny showed that the inheritance of some aspects of these behaviors is consistent with models involving single autosomal loci. The inheritance of secondary sexual characteristics in the males is also investigated. The genes for courtship behavior and secondary sexual characteristics do not assort independently. The origin of the premating isolating mechanisms may be explained by either an initial habitat separation between the two groups, or by a founding event with each group subsequently diverging in slightly different habitats. It is suggested that the differences in the microhabitats may have a profound effect on what type of signal (visual or vibratory) would be effective.

Ample evidence exists that an increase in the inbreeding level of a population reduces the value of fitness components such as fecundity and survival. It does not follow, however, that these decreases in the components of fitness impact population dynamics in a way that increases extinction risk, because virtually all species produce far more offspring than can actually survive. We analyzed the effects of the genetic quality (mean fitness) of individuals on the population growth rate of seven natural populations in each of two species of wolf spider in the genus Rabidosa, statistically controlling for environmental factors. We show that populations of different sizes, and different inbreeding levels, differ in population dynamics for both species. Differences in population growth rates are especially pronounced during stressful environmental conditions (low food availability) and the stressful environment affects smaller populations (o500 individuals) disproportionately. Thus, even in an invertebrate with an extremely high potential growth rate and strong densitydependent mortality rates, genetic factors contribute directly to population dynamics and, therefore, to extinction risk. This is only the second study to demonstrate an impact of the genetic quality of individual genotypes on population dynamics in a wild population and the first to document strong inbreeding-environment interactions for fitness among populations. Endangered species typically exist at sizes of a few hundred individuals and human activities degrade habitats making them innately more stressful (e.g. global climate change). Therefore, the interaction between genetic factors and environmental stress has important implications for efforts aimed at conserving the Earth's biodiversity.

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Understanding past as well as present selection pressures that have influenced the origin, evolution and maintenance of existing communication systems presents a considerable challenge to biologists. Among the multitude of factors known to influence signal form, characteristics of the signalling environment play a crucial role. For example, numerous empirical studies have demonstrated a clear effect of signalling habitat on visual signal evolution in fish (Endler, 1991; Endler, 1992; Boughman, 2001; Maan et al., 2006), birds (Marchetti, 1993; Endler and Thery, 1996; Cynx et al., 1998; Lengagne et al., 1999; Lengagne and Slater, 2002; Heindl and Winkler, 2003a; Heindl and Winkler, 2003b;Uy and Endler, 2004), and lizards (Fleishman and Persons, 2001; Macedonia et al., 2003; Peters and Evans, 2003; Leal and Fleishman, 2004). In addition, evidence that air-borne signal evolution is influenced by habitat characteristics is provided by studies involving singing insects (Michelsen and Larsen, 1983; Romer, 1990;VanStaaden and Romer, 1997;Schul and Patterson, 2003), birds (Richards and Wiley, 1980; Ryan and Brenowitz, 1985;Wiley, 1991) and frogs (Ryan et al., 1990; Ryan and Wilczynski, 1991). Fewer studies have assessed habitat-specific effects on the evolution of substrate-borne (seismic) signals (Michelsen et al., 1982; Magal et al., 2000; Cokl and Dober- AbstractSignals used in communication are often hypothesized to be optimally designed for their signalling environment. Here, we explore the importance of signalling substrate on seismic signal efficacy and reproductive behavior in the wolf spider, Schizocosa retrorsa: a species found on multiple signalling substrates (pine litter and/or red clay or sand). In this multimodal signalling species, simultaneous with conspicuous visual displays, males produce percussive seismic signals via an impulse mechanism which tends to excite a substrate evenly across a wide band of frequencies. We first quantified the transmission characteristics of this broadband percussive signal by playing recorded signals back across three naturally occurring substrates, two of which represent substrates upon which S. retrorsa is commonly found: leaf litter, pine litter and red clay (the latter two exemplify their natural habitat). The substrates varied in their transmission characteristics with respect to both attenuation (higher on red clay) and filtering. Next, we compared copulation success, courtship behavior and microhabitat choice among these same substrates. Copulation frequency was higher on the natural substrates of pine litter and red clay as compared with leaf litter. Males took longer to initiate courtship on leaf litter, but once initiated, courtship behavior did not vary across substrates and we were not able to discern any choice with respect to the first, or the most common, substrate chosen. Our results show that while S. retrorsa's percussive signals may not be matched to the specific properties of any one substrate, copulation success was substrate dependent and we d...