Genetic drift drives evolution in the bird-pollinated, terrestrial island endemicGrevillea georgeana(Proteaceae)

Abstract

Plant species distributed across terrestrial islands can show significant genetic divergence among populations if seed and pollen dispersal are restricted. We assessed the genetic connectivity between populations of Grevillea georgeana, restricted to seven disjunct inselbergs in semi‐arid Western Australia. The phylogeographical pattern and population genetics of populations were determined using sequence data from two plastid DNA intergenic spacers and ten nuclear microsatellite loci. The plastid DNA markers indicated high genetic differentiation among the majority of populations. Haplotypes were restricted to individual inselbergs, with the exception of two that were shared among three isolated populations that formed part of an elongated greenstone belt and that may be connected via inaccessible populations of G. georgeana. There was also strong differentiation within some of the populations, suggesting long‐term isolation and persistence of G. georgeana on these terrestrial islands. Overall, the genetic patterns suggest limited seed dispersal, with differentiation in the plastid DNA genome being driven by genetic drift. In contrast, pollen movement, although generally restricted, may occur between neighbouring populations, resulting in a pattern of isolation by distance in the nuclear markers. This potential for limited or no seed dispersal, but connectivity via pollen flow, should be considered, given that many of the inselbergs are under consideration for resource development. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178, 155–168.

Anthropogenic fragmentation may not alter pre‐existing patterns of genetic diversity and differentiation in perennial shrubs

“…Patterns of admixture and genetic relationships among populations suggest that birds facilitating pollen flow among adjacent G. caleyi ridges probably travel the shortest route between the ridges. Similar patterns of IBD have been observed for other species that occur on terrestrial islands, implying that pollen flow occurs between the closest islands (Nistelberger, Byrne, et al., ; Pinheiro et al., ).…”

“…The high levels of population differentiation and inferred inbreeding but relatively modest levels of within‐population and within‐species diversity found for both G. caleyi and G. longifolia resemble those observed in the similarly rare and fully self‐compatible G. macleayana (England, Beynon, Ayre, & Whelan, ; England et al., ; Roberts, Ayre, & Whelan, ). Higher levels of microsatellite diversity and lower population differentiation were observed for self‐incompatible species, including those that are rare and have restricted and disjunct distributions such as G. iaspicula , G. repens and G. georgeana (Hoebee, ; Hoebee & Young, ; Holmes, James, & Hoffmann, ; Nistelberger, Byrne, Coates, & Roberts, ), and even more so for the common species G. mucronulata (Forrest, Ottewell, Whelan, & Ayre, ).…”

Biodiversity hotspots and Ocbil theory

“…x Amphisopus (Isopoda : Amphisopidae) Gouws and Stewart (2013) x T w o r a r e Eremophila (Scrophulariaceae: Myoporeae) Llorens et al (2013) x Eucalyptus gomphocephala (Myrtaceae) Bradbury and Krauss (2013) x Calothamnus quadrifidus (Myrtaceae) Nistelberger et al (2015) x Eucalyptus gomphocephala (Myrtaceae) Nevill et al (2014) x Species-specific phylogeography of five west coast sand-dune and sand-plain reptiles Edwards et al (2014) x Flora reviewed Byrne et al (2014) x Millar et al (2014) Plant Soil Tapper et al (2014a) x Granite inselberg perennial herb Stypandra glauca (Hemerocallidaceae) Tapper et al (2014b) x Terrestrial fauna and flora with dated phylogenies reviewed Rix et al (2014) x Eucalyptus wandoo (Myrtaceae) Dalmaris et al (2015) x Bird-pollinated, inselberg endemic Grevillea georgeana (Proteaceae) Nistelberger et al (2015a) x Banksia sphaeorcarpa var. caesia (Proteaceae) Nistelberger et al (2015b) x Drakaea elastica (Orchidaceae) pollination ecotypes Menz et al (2014) x Erica coccinea (Ericaceae) Segarra-Moragues and Ojeda (2010) x Fossorial skinks Scelotes (Squamata: Scincidae)…”

“…Hopper (2014) x Bird-pollinated, inselberg endemic Grevillea georgeana (Proteaceae) Nistelberger et al(2015) x A u s t Hakea (Proteaceae) phylogeny, ancestral bird-pollination Mast et al (2012) Plant Soil x Hyper-specialisation for long-billed bird pollination: the malachite sunbird pollination syndrome. Geerts and Pauw (2009) x Sunbird pollinator limitation in the endangered geophyte Brunsvigia litoralis (Amaryllidaceae)…”

Conservation of old individual trees and small populations is integral to maintain species' genetic diversity of a historically fragmented woody perennial

“…Geographically isolated populations may still be connected via gene flow mediated by strong‐flying pollinators (Gonçalves‐Oliveira et al, ; Hopper, ), especially in contemporary landscapes where genetic interconnection may be facilitated by the occurrence of introduced or translocated (stepping‐stone) populations in the intervening landscape (Gevaert, Mandel, Burke, & Donovan, ). Nonetheless, some outcrop endemic plants that are pollinated by highly mobile nectar feeding birds show pollen movement that is restricted to within stands or between neighbouring populations (Bezemer, Krauss, Phillips, Roberts, & Hopper, ; Nistelberger et al, ). Further investigation is required to improve understanding of the paradox of strong genetic differentiation despite pollination systems that are predicted to facilitate genetic connectivity among isolated populations (Breed et al, ; Hopper, ).…”