High genetic diversity and population structure in the endangered Canarian endemic Ruta oreojasme (Rutaceae)

Abstract

Insular species are expected to have low genetic diversity, for their populations are often small and isolated, and characterized by restricted gene flow and increased incidence of inbreeding. However, empirical results do not always match this expectation. For example, population genetic analyses of several Canarian endemics, based mainly on allozymes, show levels of genetic diversity exceptionally high for insular species. To investigate whether genetic variation in rare species endemic to Canary Islands is low, as predicted by theoretical expectations, or high, as documented in some previous studies, we analysed genetic diversity of the endangered Ruta oreojasme, a rare endemic of the island of Gran Canaria, using microsatellite markers, which are more variable than allozymes. Our analyses identified very high levels of genetic diversity (A = 7.625, P = 0.984, H o = 0.558, H e = 0.687) for R. oreojasme. Even though the distribution of the species is restricted to the South of Gran Canaria, only one population shows low genetic diversity, isolation and signs of a recent bottleneck/founder event. Some intrinsic characteristics of R. oreojasme (hermaphroditism, proterandry and polyploidy), the relative climatic stability of the Canarian archipelago during Quaternary glacials/interglacials, the size of most populations (thousands of individuals), its age, and the relative proximity of the archipelago to the mainland might have contributed to the high diversity that characterises this endemic. As expected, given the marked topographic complexity of Gran Canaria, we found marked genetic structure in R. oreojasme populations. Our results support the observation that Canarian endemics are characterised by unexpectedly high genetic diversity and provides important insights for potential applications to the conservation of R. oreojasme.

Alpine species in dynamic insular ecosystems through time: conservation genetics and niche shift estimates of the endemic and vulnerableViola cheiranthifolia

“…For example, another Teide endemic Silene nocteolens (Sosa et al, 2011), the Canarian olive tree Olea europaea ssp. guanchica (García-Verdugo et al, 2010) and the narrow-ranged Ruta oreojasme (Meloni et al, 2015) show surprisingly high values of genetic variation. In contrast, the species within the endemic genus Bethencourtia (Rodríguez-Rodríguez et al, 2018), Ilex perado ssp.…”

Geographical distance and barriers explain population genetic patterns in an endangered island perennial

“…2015) rejected the hypothesis that island populations always have a low genetic diversity due to bottleneck effects, small population size and adaptation to specific ecological conditions (Bouzat 2010; López-Pujol et al . 2013; Meloni et al . 2015).…”

High genetic diversity and presence of genetic structure characterise the Corso-Sardinian endemicsRuta corsicaandRuta lamarmorae(Rutaceae)

“…Indeed, D est values are approximately two times larger than F ST values ( F ST =0.097, D est =0.162 for R. corsica; F ST =0.086, D est =0.179 for R. lamarmorae ), suggesting that the studied populations might be more differentiated than implied by F ST . High values of heterozygosity and lower levels of F ST than D est were also found in the congener R. oreojasme ( H e = 0.687, F ST = 0.097, D est = 0.275; Meloni et al 2015).…”

“…1), most populations showed fewer genetic signatures of isolation and small population size than typically expected for insular endemics (i.e., low gene diversity, high homozygosity, high LD; Ellstrand 1993, Frankham 1998, Bouzat 2010). Unexpectedly high values of genetic diversity were also found in the congener R. oreojasme , an endangered species endemic to the island of Gran Canaria in the Canarian archipelago ( A =7.625, P =0.984, H o =0.558, H e =0.687; Meloni et al . 2015).…”

“…2014). The relatively low genetic diversity found in R. microcarpa , resulting mainly from the almost total absence of sexual reproduction in this species (Meloni et al . 2015), highlights the role of outcrossing in maintaining variation within and among populations.…”