Volume 73 – Issue 2 (June 2008)

A total of 519 plant taxa have been added to the known flora of Great Falls Park, Fairfax County, Virginia, since the vascular flora was first published more than 30 yr ago. Species erroneously reported from the Park are noted. To date, 1,015 vascular plant taxa representing 1,002 species, eight infraspecific taxa, and five hybrids from 492 genera in 139 families have been documented within the Park. Of these, 76 are known only from historical specimens. Twenty-three of the documented plants are listed as rare in the Commonwealth of Virginia. Non-native taxa comprised 19.8% of the vascular flora in the Park. Ecological community types of the Park are described and listed for each associated taxon.

It has long been suggested that phylogenetic divergence between parental species determines the likelihood of their producing a successful polyploid, with closely related parents less likely to form a successful polyploid than more divergent parents. This suggestion has been based partly on observation of patterns of polyploid ancestry and partly by extrapolation from analyses of the processes that give rise to polyploids. Here we present a new survey of the patterns of the divergence between the parents of polyploids, based on node-based and clade-based analyses of phylogenetic trees. We also use the topology of the phylogenetic trees to inform a null expectation of the distance between parental species, assuming random crossing between all species pairs in a genus. We used molecular phylogenies now available for eight plant genera containing multiple polyploids whose parentage has been investigated: Tragopogon, Persicaria, Brassica, Leucaena, Spartina, Spiranthes, Nicotiana, and Glycine. We found that the phylogenetic distance between progenitors of polyploids did not differ significantly from the null expectation. In contrast, the distance between parents of diploid hybrids (both stable and unstable) in these genera were lower than would be expected with random crossing. We discuss how these findings may fit with recent progress, through genetic and genomic studies, in understanding the processes involved in polyploidization. 

Studies conducted in many parts of the world over the past 20 yr have shown that smoke can induce seeds to germinate, especially those of species native to fire-prone habitats. Chemicals in smoke may signal to the seed that environmental conditions are favorable for its germination and growth (Roche, Koch, and Dixon 1997). However, smoke stimulated germination appears to have developed even in some species that are not native to fireprone habitats (e.g., lettuce; Jager et al. 1996). In fire-prone habitats around the world, including the California chaparral (Keeley and Fotheringham 1997), South African fynbos (Brown et al. 2003), Western Australian shrublands (Morris 2000), and northeastern Australian savannas (Williams et al. 2005), seeds of a wide range of species germinate in response to cues from 3-methyl-2H-furo[2,3c]pyran-2-one in smoke (Flematti et al. 2004). Some plants, such as the Australian Grevillea spp., show a significant increase in germination after exposure to smoke compared to other signals such as scarification or heat shock (Morris 2000).

Lynch’s Woods Park (Newberry County, South Carolina) was floristically surveyed between 2002 and 2005. The Park features north-facing slopes, granite outcrops, and several small streams within the Piedmont physiographic province. A total of 528 vascular plant species were documented within the 101.2 ha, including 91 (17%) nonnatives. Three species, Anemone berlandieri, Eurybia mirabilis, and Rhododendron eastmanii were rare species. Analysis of community structure revealed that most of the area was a mixed mesophytic forest, with the upland sites developing toward an oak-hickory forest.

Leitneria floridana is a rare woody species with a disjunct distribution in the southeastern and south-central United States. Although the distribution of L. floridana is well established, little is known about the comparative biology of its disjunct populations or the factors contributing to its rarity. We studied populations of L. floridana in Missouri, Arkansas, Texas, and Florida to characterize and compare population density, habitat, ecophysiology, morphology, and growth. Our results show that plants of the Missouri provenance are the most unique phenotypically, plants in Texas are the fastest growing, and plants in Arkansas seem particularly adapted to shade. We found that L. floridana grows in chemically and physically diverse soils and under a broad range of insolation. Soil moisture content appears to be the most important environmental factor governing the occurrence of L. floridana, with soil moisture and distribution density positively correlated.

Clemson University has begun an ambitious undertaking in natural history as the series title ‘‘Biota of South Carolina’’ indicates. This volume is the fifth in the series and the first to deal with plants.

These laminated pocket guides are the first in a series that will eventually cover all the wild orchids of the United States and Canada.

Noteworthy Collections: Mississippi

Noteworthy Collections: Kentucky

The first edition of The Plants of Pennsylvania was published in 2000. Though it has only been seven years, significant advances in plant systematics have made this second edition a ‘‘must have’’ for serious botanists, both amateur and professional. Major changes in the second edition reflect these taxonomic reshufflings.