Strong Spatial Genetic Structure Reduces Reproductive Success in the Critically Endangered Plant Genus Pseudomisopates

Abstract

Clonal growth can be a double-edged sword for endangered species, because the short-term insurance against extinction may incur a longer-term hazard of creating small inbred populations with low fecundity. In the present study, we quantify the advantages and disadvantages of clonal growth regarding the fitness of the central Iberian monotypic endangered genus Pseudomisopates. Preliminary studies showed that the species is self-incompatible and exhibits extensive clonal growth with plants flowering profusely. However, seeds at many sites seemed to be unviable, and no seedlings have been observed in the field. A fully replicated nested sampling design (n = 100) was conducted to explore genetic (using seven SSR loci) and environmental factors potentially affecting seed viability, such as: 1) clonal and genetic diversity, 2) spatial genetic structure, and 3) environmental factors (shrub cover and grazing). Generalized Linear Mixed Models were fitted relating genetic and environmental variables to reproductive variables (seed viability and flower display). Our results indicate that the relatively low genotypic diversity of the population (PD = 0.23), as quantified by SSRs, and the strong spatial genetic structure observed are congruent with intense clonal growth. This clonal growth is enhanced by unfavorable environmental conditions, such as canopy closure and grazing. Under these circumstances, both flower display and mate availability decrease, thus hindering sexual reproduction. Indeed, a mixed reproductive system (clonal and sexual) to escape environmental stochasticity is crucial for the survival of Pseudomisopates, a species inhabiting a disturbance-prone ecosystem.

Narrow endemics in European mountains: high genetic diversity within the monospecific genus Pseudomisopates (Plantaginaceae) despite isolation since the late Pleistocene

“…The two spatially separated clusters of Pseudomisopates populations can be used as a simple system to investigate the potential impact of Quaternary climatic shifts on allopatric differentiation and maintenance of genetic diversity. The aims of the current study were: (1) to evaluate whether any of the three patterns of genetic diversity for narrow endemics (see above) accurately describes the spatio‐temporal distribution of current genetic diversity of Pseudomisopates ; (2) to compare the clonal pattern revealed by the previous SSR study (Amat et al ., ) with the results from AFLPs; and (3) to contrast the patterns of genetic diversity found in Pseudomisopates with those of other narrow endemics in European mountains.…”

“…This pattern results from the combined effects of bottlenecks and genetic drift and/or local adaptation (López‐Pujol et al ., ). These processes are further enhanced by the lack of gene flow between populations (Segarra‐Moragues et al ., ) and, in some cases, vegetative reproduction (Amat et al ., ). Spatially separate populations display limited evidence for genetic divergence either because they function as a single metapopulation (Blanco‐Pastor et al ., ), or because their separation was relatively recent (Szövényi et al ., ), or because there has been recent admixture. The recent separation and/or the maintenance of gene flow between populations (Casazza et al ., ) may counteract incipient differentiation processes, thereby avoiding bottlenecks, genetic drift and loss of genetic diversity. A dramatic reduction in genetic diversity due to extinctions and bottlenecks (del Hoyo et al ., ; Šajna et al ., ), including founder effects as a result of recent colonization (López‐Pujol et al ., ), leads to a strong loss of genetic diversity and no clear genetic structure can be inferred.…”

“…A preliminary inter‐simple sequence repeat (ISSR) analysis revealed a considerable amount of genetic variation, but no variation was found within the nuclear ribosomal internal transcribed spacers (ITS), leading to the hypothesis that this species has been affected by recent range reduction and fragmentation, rather than by recent colonization (see Vargas & García, ). In addition, rhizome‐mediated propagation of Pseudomisopates seems to result in a strong spatial genetic structuring within one of the populations, as revealed by simple sequence repeat (SSR) markers (Amat et al ., ).…”

Clonality as a driver of spatial genetic structure in populations of clonal tree species

“…Current statistical approaches to population genetic structure in a spatial context derive from the theoretical model of isolationby-distance (IBD) formulated by Sewall Wright (Wright 1943). The identification and quantification of SGS have long caught the attention of evolutionary biologists aware of its importance in the understanding of the evolutionary processes acting in plant populations (Epperson 1992;Troupin et al 2006;Pardini and Hamrick 2008;Hirao 2010;Amat et al 2013). Random genetic drift, natural selection, and restricted gene dispersal, acting in combination or solely, are the basic determinants of the intensity and dynamics of SGS (Wright 1943).…”

Factors Affecting the Distribution Pattern of Wild Plants with Extremely Small Populations in Hainan Island, China

“…Internal factors refer to the plant biological characteristics, including failures in heritability, reproduction, viability, and adaptability [9], [10]. External factors include both natural and human factors.…”