Virbia, Zaspel & Weller Table Of Contents, 2006

Zaspel, Jennifer M. & Weller Table Of Contents, Susan J., 2006, Review of generic limits of the tiger moth genera Virbia Walker and Holomelina Herrich-Schäffer (Lepidoptera: Arctiidae: Arctiinae) and their biogeography, Zootaxa 1159 (1), pp. 1-68 : 55-57

BIOGEOGRAPHY OF VIRBIA

Ancestral areas were calculated for five major clades mapped on one of the 779 MP trees ( Fig.114 ) using Hausdorf’s method ( Hausdorf 1998). These clades are present in the strict consensus tree ( Fig. 7 ) and have a Bremer support of at least 3. Individual gain and loss scores are given for each clade for each area as well as the resulting Weighted Area Index (= WAI; Table 4).

The ancestral area for Clade 1, comprised of all ingroup taxa, is most likely the southwestern United States and Mexico, Area D (WAI = 1.2; Table 4). Clade 2 includes the type species of Holomelina , H. aurantiaca , and other “typical” Holomelina phenotypes. For this clade, we again recover area D as the most likely ancestral area (WAI = 1.75; Table 4). Clade 3, which includes remaining former Holomelina species and Virbia ( Fig. 8 , 114 ), has a reconstructed ancestral area of Central South America excluding Mexico, Area E (WAI = 1.2; Table 4; Figs. 4 , Fig. 114 ). This reconstruction reflects the influence of V. latus and V. cyana as sister to the remaining species in the clade. As the placement of these two species is not stable among jack­knife analyses, this result must await confirmation. We did not reconstruct an ancestral area for Clade 4. Clade 5 consists of species in the V. opella complex and Central American species formerly placed in Holomelina . The reconstructed ancestral area for this clade is the southwestern U.S. and Mexico (WAI = 1; Table 4). Clade 6 consists of typical Virbia species , the area western South America (Andean region) including Colombia receives the highest WAI (1.31; Table 4).

Our WAA analysis suggests an ancestral area of the southwestern United States and Mexico for the genus Virbia (Clade 1). The species distributed in North America north of Mexico represent a composite fauna of two lineages (Clade 2, Clade 5) that dispersed northward from the southwestern U.S. and Mexico (Clades 1, 3) with subsequent vicariance events occurring within those clades. These dispersal events could represent responses to glaciation cycles, however, phylogeographic studies of the North American avifauna suggest that current bird species pairs are older than these cycles ( Klicka & Zink 1997). Similar studies of North American Virbia are needed to confirm or reject the hypothesis that their speciation was fueled by climate change.

The remaining, neotropical Virbia appear to have invaded South America just once, concomitant with the evolution of the black and yellow phenotype. This phenotype coincides with the black and yellow mimicry rings of the notodontid tribe Josiini ( Miller 1996) , but the chemistry underlying this mimicry (whether Batesian or Müllerian) is unknown.

Our biogeographic findings are not surprising given the distribution of species and areas ( Fig. 114 , Appendix 2). However, any other method of reconstructing areas for this node would result in an ambiguous reconstruction for Clade 1 given the conflicting reconstructions at Clades 2 (Area D) and 3 (Area E) ( Fig. 114 ). Further refinement of biogeographic patterns will require a species level revision of the genus.

Figures

FIGURE 4. Map of biogeographic areas. Areas: A = western USA & Canada, B = central USA & Canada, C = eastern USA & Canada, D = southwestern USA & Mexico, E = central America, F = western South America, G = eastern & central South America, H = highlands of northern South America.

FIGURE 7. Strict consensus of 123 trees L = 1356, CI = 0.47, RI = 0.65 resulting from the analysis of male­female pairs MF. Parallel lines = species placed in Holomelina, Solid lines = species placed in Virbia, Broken lines = outgroups..

FIGURE 8. Strict consensus of 779 trees L = 1698, CI = 0.41, RI = 0.65 resulting from the analysis of all taxa AT matrix. Numbers below the branch are decays, and unlabelled branches have a decay of 3. C1 ­ C6 = Clades 1 through 6. Parallel lines = species placed in Holomelina, Solid lines = species placed in Virbia, Broken lines = outgroups.

FIGURE 114. One of 779 shortest trees showing ancestral areas for five clades, B = central US and Canada, D = southwestern US and Mexico, E = Central America, F = western South America. Red = species originally placed in Holomelina, Blue = species placed in Virbia, Black = outgroups.