Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: Justin A. Porter x
Clear All Modify Search
Free access

Justin A. Porter, David Berle and Hazel Y. Wetzstein

Accurate mapping, inventory assessment, and habitat descriptions are critically important for the development of plant conservation strategies of rare plants. Georgia plume, Elliottia racemosa (Ericaceae), is a rare threatened plant endemic only to the state of Georgia. In this study, census and distribution data were collected and the ecological habitat characterized for all known populations of georgia plume using geographic information system/global positioning system (GIS/GPS)-based methods. Causes for population losses and decline were assessed by evaluating both extant populations and historically reported but currently inactive sites. Landowner permission was obtained to visit 56% (32 of 57) of all known recorded populations. Over 40% of visited locations no longer contained georgia plume; 58% of inactive sites were associated with anthropogenic disturbances including farming and timber. Populations not visited by ground were evaluated using aerial photographs: of 29 putative populations, 66% were judged highly unlikely to contain georgia plume based on current land use. Census data verified that many populations have few individuals: 75% contained less than 45 individuals; over one-third contained 12 or fewer individuals. Over 80% of extant populations had an area of less than 0.3 ha. Field and aerial assessments of recent and historically noted populations confirm that georgia plume has disappeared from many previously reported locations and that fewer than two dozen populations may remain.

Free access

Hazel Y. Wetzstein, Weiguang Yi, Justin A. Porter and Nadav Ravid

Pomegranate trees (Punica granatum) produce large numbers of both hermaphroditic (bisexual) flowers that produce fruit and functionally male flowers that characteristically abort. Excessive production of male flowers can result in decreased yields resulting from their inability to set fruit. Within hermaphroditic flowers, sex expression appears to follow a spectrum ranging from those exhibiting strong to weak pistil development. Unknown is the scope that flower quality plays in influencing fruit production. A description of floral characteristics and how they vary with flowers of different sizes and positions is lacking in pomegranate and was the focus of this study. Furthermore, the effects of flower size and position on fruit set and fruit size were evaluated. This study documents that flower size characteristics and ovule development can be quite variable and are related to flower type and position. Single and terminal flowers within a cluster were larger than lateral flowers. In addition, lateral flowers exhibited a high frequency of flowers with poor ovule development sufficient to negatively impact fruiting in that flower type. Ovule numbers per flower were significantly influenced by flower size with more ovules in larger flowers. Pollination studies verified significantly higher fruit set and fruit weight, and larger commercial size distributions were obtained with larger vs. smaller flowers. Thus, flower quality is an important issue in pomegranate. Cultural and environmental factors that influence flower size and vigor may have a direct consequence on fruit production and yield.

Free access

Justin A. Porter, Hazel Y. Wetzstein, David Berle, Phillip A. Wadl and Robert N. Trigiano

Georgia plume, Elliottia racemosa (Ericaceae), is a small tree endemic only to the state of Georgia, where it is listed as a threatened species. Information about genetic relatedness is critical for establishing approaches for safeguarding, reintroduction, and conservation of this rare species. The genetic relationships among and within selected georgia plume populations were evaluated using random amplified polymorphic DNA (RAPD) in conjunction with site visits at which time a census and GPS survey were conducted. Populations ranged from those containing eight to over 1000 individuals with most populations containing few plants (less than 50 individuals). With one exception, small populations with less than 50 individuals had more genetic similarity than populations with greater numbers of plants. Two protected populations containing large numbers of individuals were sampled extensively. Genetic similarity of individuals was not associated with plant proximity within a population. The small number of individuals and geographic isolation characteristic of many populations were associated with high within-population genetic similarity. Conservation priorities should be given to preserving as many different populations as possible to retain the genetic diversity of the species. Whether the narrow genetic variation found in some populations may be contributing to lack of sexual reproduction in the wild is an area for further study.