High biogeographical and evolutionary value of Canary Island pine populations out of the elevational pine belt: the case of a relict coastal population

Abstract

Aim Marginal populations are frequently neglected in static views of vegetation types, particularly when defining conservation reserves. The biogeographical and evolutionary importance of a marginal and endangered population of Pinus canariensis is addressed in this study to ascertain the need for conservation action. Diversity loss between adults and offspring and patterns of seed dispersal and recruitment were examined to provide evidence of recent degradation of marginal P. canariensis pinewoods. The scientific basis for the provision of sound conservation policies was investigated by elucidating the factors responsible for significant population structure.Location An isolated low-density pinewood community confined to the Arguineguin ravine, in south Gran Canaria, Canary Islands.Methods Two cohorts, of centenary trees (those older than 100 years) and young recruits, respectively, were found in a detailed inventory of the pine population in the Arguienguin ravine. Chloroplast and nuclear microsatellites were compared to assess the levels of genetic diversity between adults and recruits. Spatial genetic structure and parentage analysis based on highly polymorphic nuclear and chloroplast microsatellites were examined to test limitations in seed dispersal. The underlying environmental factors that led to a clustering effect in the population were tested using point pattern methodologies.Results Centenary trees retain high levels of genetic diversity and effective population size, suggesting a wider extension of the pinewood forests in the past. A significant loss of genetic diversity was detected between adults and recruits. Pinus canariensis dispersal distances were among the longest ever reported for anemochorous species, suggesting that environmental factors account for recruit clustering. Cluster models showed that recruits tend to aggregate in dry streambeds, where soil and water accumulation favours establishment.Main conclusions Boundary populations of P. canariensis are subjected to fragmentation and reduction in effective population size as a result of human impact. Marginal populations were denser in the past and currently require specific conservation efforts. A severe reduction in genetic diversity compromises the future of present populations. Streambeds appear to play a major role in recruit establishment, but data suggest the absence of limitations to seed dispersal.

High seed dispersal ability of Pinus canariensis in stands of contrasting density inferred from genotypic data

“…Seeds are wind-dispersed and they can potentially travel long distances providing the species with a very efficient mechanism of gene flow. Consistently with this, molecular studies have shown effective gene flow among islands (Vaxevanidou et al, 2006) and evidence of recent range expansions (López de Heredia et al, 2014).…”

“…Other factors, such as shade tolerance or competition with the understory (Otto et al, 2010) may be more important in dense humid pinewoods in order to explain the patterns of recruitment. In low density forests from arid environments, such as site 2, where evidence of local adaptation to drought was found , López de Heredia et al (2010) showed strong evidence for clustering of recruits on hygrophilous stream beds.…”

Understanding long-term post-fire regeneration of a fire-resistant pine species

“…This continuous supply of seeds allows a transient seed bank throughout the year, offsetting the problem of rapid loss of seed viability on the ground, which is typical of many pine species on field conditions (Keeley and Zedler 1998). Additionally, seeds can be wind dispersed over distances of 1.6 km, allowing low-productive stands to receive seed inputs from near high-productive stands (López de Heredia et al 2010). As a result of this pattern, Canarian pine forests always appear to have available seeds, both in the canopy and on the ground, able to germinate at any time of the year.…”

Signatures of volcanism and aridity in the evolution of an insular pine (Pinus canariensis Chr. Sm. Ex DC in Buch)

“…Our results with the MFDM test (Li, 2011) revealed that indirect demographic effects, such as a probable bottleneck produced by the catastrophic volcanic episodes of the Roque Nublo eruptive period (c. 5.5-3.5 My BP), may have shaped observed genetic diversity patterns in P. canariensis. Since the Roque Nublo episode, Gran Canaria has been more stable in terms of volcanic activity (Anguita et al, 2002); however, the impact of human activity and xericity on pine populations is higher than in the other islands (Ló pez de Heredia et al, 2010). High pollen and seed dispersal ability allow for a fast recovery of the genetic diversity of P. canariensis populations after volcanic disturbance (Navascués and Emerson, 2007).…”

“…It has an altitudinal range from 200 to 2400 m a.s.l., and it is able to live in volcanic lava flows or pyroclastic deposits of salic nature (del Arco et al, 1992;Pérez de Paz et al, 1994;Climent et al, 2002). P. canariensis exhibits a remarkable propensity for colonization, particularly in open forests resulting from disturbed pinewoods (Ló pez de Heredia et al, 2010) or during the early stages of newly developed bare soils. The invasive character of the species results in extensive gene flow (Schiller et al, 1999;Gó mez et al, 2003;Navascués et al, 2006;Vaxevanidou et al, 2006;Navascués and Emerson, 2007) and a lack of population genetic structure.…”