Patterns of pollen dispersal in a small population of the Canarian endemic palm (Phoenix canariensis)

Abstract

The genetic diversity of small populations is greatly influenced by local dispersal patterns and genetic connectivity among populations, with pollen dispersal being the major component of gene flow in many plants species. Patterns of pollen dispersal, mating system parameters and spatial genetic structure were investigated in a small isolated population of the emblematic palm Phoenix canariensis in Gran Canaria island (Canary Islands). All adult palms present in the study population (n ¼ 182), as well as 616 seeds collected from 22 female palms, were mapped and genotyped at 8 microsatellite loci. Mating system analysis revealed an average of 5.8 effective pollen donors (N ep ) per female. There was strong variation in correlated paternity rates across maternal progenies (ranging from null to 0.9) that could not be explained by the location and density of local males around focal females. Paternity analysis revealed a mean effective pollen dispersal distance of B71 m, with B70% of effective pollen originating from a distance of o75 m, and 90% from o200 m. A spatially explicit mating model indicated a leptokurtic pollen dispersal kernel, significant pollen immigration (12%) from external palm groves and a directional pollen dispersal pattern that seems consistent with local altitudinal air movement. No evidence of inbreeding or genetic diversity erosion was found, but spatial genetic structure was detected in the small palm population. Overall, the results suggest substantial pollen dispersal over the studied population, genetic connectivity among different palm groves and some resilience to neutral genetic erosion and subsequently to fragmentation.

Small but not isolated: a population genetic survey of the tropical tree Cariniana estrellensis (Lecythidaceae) in a highly fragmented habitat

“…As has been documented for other outcrossing species in small populations (Balloux, 2004;Saro et al, 2014), we observed an excess of heterozygotes in all life stages of C. estrellensis. Owing to the relatively large range of pollen dispersal, one could expect an effective mixing of genes by pollen flow or even seed dispersal within the studied population, hampering SGS.…”

“…However, immigration rates, most notably for seeds, and mean gene dispersal distances, principally for pollen, were inconsistent between fractional paternity analysis and categorical paternity assignments (Tables 2-5). A discrepancy between paternity approaches has been reported in other mating studies for tree species in small populations (Ottewell et al, 2012;Saro et al, 2014), and this difference likely arises owing to the nature of each analytical approach (Burczyk et al, 2002;Kalinowski et al, 2007).…”

“…A lack of biparental inbreeding-or any inbreeding (Table 2)-in the studied population can be explained by the absence of SGS in the adult generation and by the occurrence of pollen flow over long distances. This is in contrast to several other fragmented tree species that have shown elevated levels of mating between related individuals (Ismail et al, 2012;Tambarussi, 2013), genetic structuring (Dubreuil et al, 2010;Ismail et al, 2012;Saro et al, 2014) and inbreeding (Fuchs et al, 2003;Jump and Peñuelas, 2006;Kettle et al, 2007;Dick et al, 2008;Vranckx et al, 2011;Zhang et al, 2012;Tambarussi, 2013;Finger et al, 2014).…”

“…Indeed, even in a highly fragmented landscape, we observed a moderate to high frequency (23.5-53%) of gene immigration, indicating that pollen movement beyond the boundaries of the small fragment can reach distances 41 km (i.e., the distance between the small studied population and the nearest pollen source). Gene flow by pollen dispersal beyond the edges of seemingly isolated forest fragments has been reported for several plant species, including species that are animal-pollinated (Nason and Hamrick, 1997;Dow and Ashley, 1998;Dick et al, 2003;Sato et al, 2006;Nazareno and Carvalho, 2009;Buschbom et al, 2011;Ottewell et al, 2012;Côrtes et al, 2013;Tambarussi, 2013;Saro et al, 2014).…”

NMπ—improved re‐implementation of NM+, a software for estimating gene dispersal and mating patterns

“…Some years ago, the neighbourhood model was implemented in the NM+ software (Chybicki & Burczyk, ). The software has been successfully applied in a number of studies (e.g., Llorens, Byrne, Yates, Nistelberger, & Coates, ; Sampson, Byrne, Gibson, & Yates, ; Saro, Robledo‐Arnuncio, González‐Pérez, & Sosa, ). However, the fixed structure of the program makes it of limited applicability to specific study designs or questions (e.g., Chybicki & Burczyk, ; Lagache, Klein, Ducousso, & Petit, ).…”