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Infraspecific systematic relationships of Sarracenia alata Wood. (Sarraceniaceae) inferred from nuclear ribosomal DNA sequences.

Article Excerpt
ABSTRACT

Yellow trumpets, Sarracenia alata, is an insectivorous perennial herb that occurs infrequently in acidic hillside seepage bogs and wet savannas from central Texas to southern Alabama. Its overall range is disjunct with the western portion extending from central Texas to western Louisiana and the eastern portion extending from southeastern Louisiana to southern Alabama. Phylogenetic analysis using combined nuclear ribosomal Internally Transcribed Spacer 2 and large ribosomal subunit 26S rRNA gene DNA sequences suggest that the two disjuncts are not phylogenetically distinct from each other. It is speculated that the present range of S. alata is the result of recent migrations facilitated by rare longdistance seed dispersal events. Because these events likely have occurred only since the beginning of the Holocene, insufficient time has elapsed to bring about detectable evidence of molecular divergence between the two disjuncts of S. alata, at least with the two genes used in this study.

Introduction

Yellow trumpets, Sarracenia alata, is an insectivorous perennial herb that occurs infrequently in acidic hillside seepage bogs and wet savannas from central Texas to southern Alabama (Wherry, 1929; McDaniel, 1971; MacRoberts and MacRoberts, 1988). Its range is disjunct with the western portion extending

Although there are no obvious morphological characters that consistently distinguish eastern from western disjuncts of Sarracenia alata (Sheridan, 1991), various leaf color forms among individual populations occur. Mature leaves are typically green with reddish veins near the peristome and hood. However, some Mississippi populations in the eastern disjunct exhibit distinctive dark rose from central Texas to western Louisiana and the eastern portion extending from southeastern Louisiana to southern Alabama (Fig. 1). The closest distance between these two disjuncts is approximately 310 km. According to Sheridan (1991), the two disjuncts are separated by alluvial soil of the Mississippi River basin that is unsuitable for S. alata and is the primary factor for its absence there, coloration.

[FIGURE 1 OMITTED]

Of the named species of Sarracenia, only S.purpurea and S. rubra have been divided into subspecific taxa. In the case of S. rubra, each of five recognized subspecies (sensu Kartesz & Meacham, 1999) are disjunct and can be distinguished morphologically (Schnell, 1977)

The two recognized subspecies of S. purpurea (sensu Kartesz & Meacham, 1999) are morphologically distinct (Wherry, 1972, 1973; Schnell 1979; Ellison & Parker, 2002) but they are not disjunct (Kartesz & Meacham, 1999). However, two morphologically distinct varieties, S. purpurea ssp. purpurea var. montana (Cf. Schnell & Determann, 1997) and S. purpurea ssp....