Cycad biodiversity in the Bahamas Archipelago and conservation genetics of the threatenedZamia lucayana(Zamiaceae)

Abstract

A conservation assessment for the three cycad species native to the Bahamas Islands is presented. Results are based on field surveys on all islands where these species occur. Zamia angustifolia is native to Eleuthera, Zamia integrifolia is native to Abaco, Andros, Eleuthera, Grand Bahama and New Providence, and Zamia lucayana is endemic to Long Island. Z. angustifolia is of the highest conservation concern because of the small number of adult plants, its restricted distribution and the extensive development occurring within its habitat. Z. integrifolia also has a restricted distribution on Eleuthera and Grand Bahama and, although threatened by urban development in New Providence, it is relatively common on Abaco and Andros. Z. lucayana comprises three populations within a narrow strip of land of c. 1 km 2 ; we propose a reassignment of its current conservation status from Endangered to Critically Endangered. We assessed the genetic structure of Z. lucayana based on 15 polymorphic microsatellite DNA loci; this indicated that the three known populations should be considered a single management unit. However, the high number of private alleles suggests that genetic drift, indicative of recent fragmentation, is progressing. We propose in situ conservation strategies, and we also collected germplasm from a total of 24 populations of these three cycad species, for ex situ conservation.

Will the same ex situ protocols give similar results for closely related species?

“…This species is now considered critically endangered due to small population size, limited extent of occurrence, and pressure from residential development and sand mining (Calonje et al 2013). Conservation genetic analysis indicates that Z. lucayana has significant genetic structure as seen via analysis of molecular variance, but is considered a single population for management purposes (Calonje et al 2013). Zamia species, and cycads in general are ideal candidates for ex situ conservation given slow reproductive cycles, concerns with poaching, and recalcitrant seeds (BGCI 2015).…”

“…Population size: bay rush has a single population of ca. 1000 plants (Calonje et al 2013), whereas sinkhole cycad populations do not exceed 200 plants, and less than 500 plants are known (Calonje et al 2009b). Reproductive differences: Caribbean zamias (from Florida and the West Indies), such as bay rush, have distinctively different life histories than rainforest cycads such as sinkhole cycad, as Caribbean zamias reach reproductive maturity faster and produce reproductive structures more often than rainforest zamias Clugston et al in press).…”

“…In addition to these biological and geographic factors, we selected these two species for logistic reasons. Both are especially well suited for the current study due to abundant, well curated ex situ collections available, and detailed documentation of provenance (Calonje et al 2009b(Calonje et al , 2013.…”

“…Thorough sampling of leaflets of in situ individuals from throughout the native populations was performed, as detailed in Calonje et al (2013) and Griffith et al (2015), and summarized here and in Table 1. Leaflet samples from dispersed individuals covering the geographic span of the subpopulations were collected and labelled, with an emphasis on even spatial distribution.…”

“…The ex situ collection is seed-grown from in situ female plants. Within the single population, bay rush has three major sub-populations, termed Buckley's, Hamilton's and Petty's (Calonje et al 2013). We compared these three in situ sub-populations to living collections developed from seeds collected during fieldwork in 2009.…”