Landscape genetics reveals inbreeding and genetic bottlenecks in the extremely rare short-globose cacti Mammillaria pectinifera (Cactaceae) as a result of habitat fragmentation

Abstract

Mammillaria pectinifera is an endemic, short-globose cactus species, included in the IUCN list as a threatened species with only 18 remaining populations in the Tehuacán-Cuicatlán Valley in central Mexico. We evaluated the population genetic diversity and structure, connectivity, recent bottlenecks and population size, using nuclear microsatellites. M. pectinifera showed high genetic diversity but some evidence of heterozygote deficiency (FIS), recent bottlenecks in some populations and reductions in population size. Also, we found low population genetic differentiation and high values of connectivity for M. pectinifera, as the result of historical events of gene flow through pollen and seed dispersal. M. pectinifera occurs in sites with some degree of disturbance leading to the isolation of its populations and decreasing the levels of gene flow among them. Excessive deforestation also changes the original vegetation damaging the natural habitats. This species will become extinct if it is not properly preserved. Furthermore, this species has some ecological features that make them more vulnerable to disturbance such as a very low growth rates and long life cycles. We suggest in situ conservation to prevent the decrease of population sizes and loss of genetic diversity in the natural protected areas such as the Tehuacán-Cuicatlán Biosphere Reserve. In addition, a long-term ex situ conservation program is need to construct seed banks, and optimize seed germination and plant establishment protocols that restore disturbed habitats. Furthermore, creating a supply of living plants for trade is critical to avoid further extraction of plants from nature.

Genetic diversity and differentiation among Prosopis alba (Leguminosae) populations from dry valleys of Bolivia with different levels of human disturbance and altitude

“…In recent bottleneck, the rare alleles are the first to be lost diminishing the mean number of alleles per locus. In contrast, heterozygosity is less affected generating a transient excess of heterozygosity compared to that expected given the resulting numbers of alleles (Cornuet & Luikart, 1996;Luikart & Cornuet, 1998;Maya Garcia et al, 2017). A reduction in genetic diversity is predicted during forest movement as a result of bottlenecks occurring throughout the range expansion (Newton, Allnut, Gillies, Lowe, & Ennos, 1999;Williams & Arnold, 2001).…”

Genomic data of different resolutions reveal consistent inbreeding estimates but contrasting homozygosity landscapes for the threatened Aotearoa New Zealand hihi

“…Mating between close relatives may reduce fitness in offspring, an effect attributed to the unmasking of deleterious recessive mutations in regions of the genome that are rendered identical by descent (IBD; Bosse et al, 2019; Charlesworth & Charlesworth, 1987). Whilst inbreeding is generally undesirable, the stakes are especially high in at‐risk species, for example where genetic diversity has been reduced by severe bottlenecks or habitat fragmentation (Maya‐Garcia et al, 2017). For these reasons, estimation of the inbreeding coefficient ( F ) is commonly used in ecology, evolution and conservation biology where it may be employed as a proxy for adaptive potential and to inform population management strategies (Hoffmann et al, 2017).…”

Landscape genetics of Mexican biodiversity: A review

“…All studies found evidence of barriers to gene flow for both animals and plants (figure 2). However, several studies used barrier detection analysis as an explorative tool, as opposed to hypotheses driven (e.g., Maya-García et al, 2017;Rojas-Méndez et al, 2017). is means that few studies stated a priori hypotheses of specific landscape features, acting as barriers to gene flow, and explicitly acknowledged where to find the hypothesized barriers in the landscape.…”