High levels of genetic variability and inbreeding in two Neotropical dioecious palms with contrasting life histories

Abstract

We characterized the population genetics of two Neotropical dioecious palm species of Chamaedorea with contrasting life strategies from the region that is both the northernmost extent and most species rich of the genus. Chamaedorea tepejilote is a common, wind-pollinated arboreal understory palm. Although most adult plants reproduce each year, only a few individuals produce the majority of flowers and seeds. Chamaedorea elatior, conversely, is an uncommon climbing subcanopy palm with entomophilous flowers (insect-pollinated characteristics). Most of the mature palms do not reproduce in consecutive years and fruiting is episodic. Isozymes with a total of 107 alleles for 27 loci of 17 enzymes from six populations were assessed. For both species, cooccurrence of high levels of genetic variation and homozygosity was observed (C. tepejilote: He: 0.385-0.442, f: 0.431-0.486; C. elatior: He: 0.278-0.342, f: 0.466-0.535). Genetic differentiation of C. elatior was much lower (y ¼ 0.0315) than that for C. tepejilote (y ¼ 0.152). The contrast in differentiation may be influenced by differences in the spatial scale of the genetic neighborhoods of the two species. The simultaneous maintenance of inbreeding and of a large number of alleles within the populations is attributable to the low and variable number of mating pairs. Demographic studies indicate that this pattern could be explained by low reproductive frequency among individuals and over years in C. elatior and by reproductive dominance in C. tepejilote.

Disturbance and Resilience in Tropical American Palm Populations and Communities

“…Both pollen and seed dispersal are constrained by a number of ecological factors including density and aggregation of individuals, effects of habitat heterogeneity (Vormisto, 2000;Vormisto et al, 2000;Svenning, 2001) and predation (Janzen, 1970), all of which result in the establishment of descendents (Luna et al, 2005). For plant populations, total gene dispersal is composed of pollen dispersal (pollination) and seed dispersal; the latter contribute twice as much to gene dispersal because pollen is haploid while the embryo is diploid (Slatkin, 1985;Hamilton, 1999).…”

“…Early botanists thought that palms were wind pollinated (reviewed by Henderson, 1986). While anemophily has been confirmed in several palms (Listabarth, 1992b;Luna et al, 2005;Savolainen et al, 2006), a large body of data on palm entomophily has accumulated over the last decades (e.g. Henderson, 1986;Anderson et al, 1988;Barfod, 1988;Silberbauer, 1990;Olesen & Balslev, 1990;Ervik, 1993;Listabarth, 1992aListabarth, , 1993Listabarth, , 1996Bernal & Ervik, 1996;Couturier et al, 1997;Ervik et al, 1999;Otero & Oyama, 2001;Nuñez et al, 2005;Nuñez & Rojas, 2008).…”

“…Genetic studies of palm resilience are all at the population level, and are limited to a few case studies (Euterpe edulis, Galetti et al, 2006;Iriartea deltoidea, Sezen et al, 2007). Some studies compare different species but not in a context of disturbance, so that interspecific differences in resilience abilities are only hypothesized (Luna et al, 2005(Luna et al, , 2007.…”

“…Genetic studies on palm populations of Euterpe edulis (Cardoso et al, 2000;Conte et al, 2003;Gaiotto et al, 2003), Chamaedorea spp. (Cibrián-Jaramillo et al, 2009;Luna et al, 2005;Luna et al, 2007), Astrocaryum mexicanum (Eguiarte et al, 1992), Bactris gasipaes var. chichagui , Oenocarpus bataua (Montúfar, 2007), Ceroxylon echinulatum (Trénel et al, 2008) have reported high levels of genetic variation in comparison to other tropical trees.…”

Conservation genetics and ecology of an endemic montane palm on Lord Howe Island and its potential for resilience

“…Low genetic variation is expected for isolated endemic species with small population size (Young and Clarke 2000;Leimu et al 2006). The level of genetic diversity within L. mooreana was moderate compared with other endemic or rare palm species (Dowe et al 1997;Shapcott 1998;González-Pérez et al 2004;Henderson et al 2006;Shapcott et al 2007Shapcott et al , 2009, other more widespread species present on LHI (Savolainen et al 2006;Babik et al 2009) and widespread palm species elsewhere (e.g., Eguiarté et al 1992;Luna et al 2007), indicating some potential for genetic resilience.…”