Does genetic variation and gene flow vary with rarity in obligate seeding Persoonia species (Proteaceae)?

Abstract

Theory predicts that genetic variation is a determinant of persistence, and that the abundance and distribution of variation is strongly dependent on genetic drift and gene flow. Small, isolated populations are expected to be less diverse and more differentiated than large, inter-connected populations. Thus rare species may be more at risk of extinction. We used 389 putative AFLP loci to compare genetic variation and structuring in two pairs of closely-related common (large populations geographically widespread) and rare (small populations spatially restricted) Persoonia species. We genotyped 15-22 adult plants, from four populations, covering the geographic range of each species. Although genetic diversity was low for all four species (for long-lived outcrossing perennials), we found significantly more diversity within populations of the rare species than within those of the common species. AMOVA revealed significant levels of structure both among species (21%) and populations (15%). The proportion of inter-population variation within species did not vary consistently with rarity (Pair 1 rare 21.1% versus common 16.5%; Pair 2 rare 15.8% versus common 20.6%). However populations of the rare species were more differentiated than common species with similar geographic separation, suggesting greater gene flow between populations of the common species. Therefore, even relatively small genetically isolated populations of rare Persoonia species were more diverse than large populations of common Persoonia species. We hypothesise that common Persoonia species have undergone a rapid range expansion from a narrow gene pool, while genetic diversity is maintained in the soil seed-bank of rare remnants.

Remarkable Resilience of Forest Structure and Biodiversity Following Fire in the Peri-Urban Bushland of Sydney, Australia

“…Urbanization will also impact animal populations that pollinate flowers and disperse propagules. A narrow geographical range and disjunct occurrences within fragmented remnants heightens the risk of extinction due to stochastic events, reduced genetic variability, reproductive failure and dispersal boundaries [85,86]. More detailed investigation of species' traits associated with recovery and resilience to fire and other disturbances will improve future adaptive management in the face of accelerating threats to biodiversity [87].…”

Dispersal and recruitment dynamics in the fleshy-fruited Persoonia lanceolata (Proteaceae)

“…The question remains as to whether these dispersal agents have the ability to move seeds between populations, especially in order to prevent local population extinctions under a regime of too frequent fire. It has been suggested that vertebrate dispersal of Persoonia seeds may be a mechanism for gene flow between populations (Rymer & Ayre 2006) or for re-establishment of populations after local extinction (French & Westoby 1996).…”

Genetic variation relevant for the conservation of the narrow endemic Senecio carbonensis (Asteraceae) from the southern Andes

“…1986), and life‐history attributes of the species (Premoli 1997; Premoli et al . 2001; Rymer & Ayre 2006). Given that phylogenetic relatedness of species may have important effects on the outcome of comparative studies (Harvey & Pagel 1991), growing interest exists in conservation genetic studies comparing phylogenetically close congeneric species that differ in abundance/forms of rarity (e.g.…”

“…However, there are also cases in which genetic variation is relatively high for rare species (Linhart & Premoli 1993), even within extremely narrowly distributed taxa (Soltis & Soltis 1991;Cosner & Crawford 1994;Lewis & Crawford 1995). Nevertheless, results may differ depending on the criteria used to determine rarity, which is generally based on local abundance, geographic range and habitat specificity (Rabinowitz 1981;Rabinowitz et al 1986), and life-history attributes of the species (Premoli 1997;Premoli et al 2001;Rymer & Ayre 2006). Given that phylogenetic relatedness of species may have important effects on the outcome of comparative studies (Harvey & Pagel 1991), growing interest exists in conservation genetic studies comparing phylogenetically close congeneric species that differ in abundance/ forms of rarity (e.g.…”

“…Several surveys of isozyme variation in plants have shown that rare, endemic or narrowly distributed plants tend to maintain lower isozyme variation than widespread species (Karron 1987; Hamrick & Godt 1989, 1996; Premoli 1997; Gitzendanner & Soltis 2000), and have limited ability to adapt to changing environmental conditions (Rymer & Ayre 2006). However, there are also cases in which genetic variation is relatively high for rare species (Linhart & Premoli 1993), even within extremely narrowly distributed taxa (Soltis & Soltis 1991; Cosner & Crawford 1994; Lewis & Crawford 1995).…”