Butterflies of the upper Frio-Sabinal region, central Texas, and distribution of fauna elements across the Edwards Plateau.By Gaskin, D.E.
Gaskin, D.E. 1998. Butterflies of the upper Frio-Sabinal region, central Texas, and distribution of fauna elements across the Edwards Plateau. Journal of the Lepidopterists' Society, 52(3): 229-261.
ABSTRACT. A survey of the butterfly fauna (1988-96) of the upper Frio-Sabinal region of the southern Edwards Plateau, Texas, is presented. Butterflies were observed along transects at five study sites and during repeated opportunistic transects at 12 secondary localities. A total of 28,03.5 specimens, comprising 100 species was recorded. Another 51 species were reported by other lepidopterists working 1.5-25 km south of this region during the same period; most were collected from the vicinity of Concan, in north-central Uvalde Co. Twenty-seven species recorded in the upper Frio-Sabinal region were represented by 1-5 specimens only. Simple approximation models were used to estimate the proportion of the theoretical' total species collected to date at the upper Frio-Sabinal site. No statistically significant differences were found between the geographical components at the Frio-Upper Sabinal site and two other well-worked sites; Barton Creek (Travis Co.) and Concan (N. Uvalde Co,). Composition and distribution patterns of the butterfly fauna across the Edwards Plateau were examined by analyzing data from 16 reasonably well-collected counties. Geographically, the butterfly fauna across the Edwards Plateau has a strong W/SW trans-Pecos component in Brewster and neighboring counties, which is only weakly represented in the north and east. A S/SE element is significant only along the Balcones fault region from Uvalde to Travis counties, while a NE/E element is numerically important but decreases sharply west of Real and Uvalde counties. Both are associated with the riparian corridors of the southeast. A N/NW element is widespread, but only weakly represented in all counties. Disturbed habitats were dominated by Pieridae (64%). Intergrading dry, subtropical habitats, dry montane woodland areas, coastal woodlands and southern tropical woodlands were dominated by Hesperiidae (4.5-7.5%). Richest ecological zones were the south tropical woodlands (49 species), dry subtropical forest and scrub (32 species) and Great Plains savanna habitats (16 species). Other ecological zones were characterized by 12 species or less. The Hesperiidae was the best represented family (97 species) and the Pyrginae the most abundant subfamily (.53 species). There is little endemism in the butterfly fauna of Edwards Plateau. The relative species richness (227, with 3.5 more in Brewster Co. only) can be attributed largely to its strategic geographical position. It is difficult to specify any one element on the Plateau which could truly be said to be characteristic of the butterfly fauna, because so many of these species reach a range limit at some point on the Plateau.