Spatial and temporal genetic structure in a hybrid cordgrass invasion

Abstract

Invasive hybrids and their spread dynamics pose unique opportunities to study evolutionary processes. Invasive hybrids of native Spartina foliosa and introduced S. alterniflora have expanded throughout San Francisco Bay intertidal habitats within the past 35 years by deliberate plantation and seeds floating on the tide. Our goals were to assess spatial and temporal scales of genetic structure in Spartina hybrid populations within the context of colonization history. We genotyped adult and seedling Spartina using 17 microsatellite loci and mapped their locations in three populations. All sampled seedlings were hybrids. Bayesian ordination analysis distinguished hybrid populations from parent species, clearly separated the population that originated by plantation from populations that originated naturally by seed and aligned most seedlings within each population. Population genetic structure estimated by analysis of molecular variance was substantial (F ST ¼ 0.21). Temporal genetic structure among age classes varied highly between populations. At one population, the divergence between adults and 2004 seedlings was low (F ST ¼ 0.02) whereas at another population this divergence was high (F ST ¼ 0.26). This latter result was consistent with local recruitment of self-fertilized seed produced by only a few parental plants. We found fine-scale spatial genetic structure at distances less than B200 m, further supporting local seed and/ or pollen dispersal. We posit a few self-fertile plants dominating local recruitment created substantial spatial genetic structure despite initial long-distance, human dispersal of hybrid Spartina through San Francisco Bay. Fine-scale genetic structure may more strongly develop when local recruits are dominated by the offspring of a few self-fertile plants.

Population structure of the Chagas disease vector, Triatoma infestans, at the urban–rural interface

“…Each of the hypotheses results in a distinct population genetic pattern under an idealized model, which when compared to the empirically observed pattern can be used to infer the routes of dispersal. Spatial patterns of genetic diversity within populations are indicative of the origin, evolutionary history, and population dynamics and allow the reconstruction of a population's migratory history (Sakai et al 2001;Bronnenhuber et al 2011;Gaudeul et al 2011;Sloop et al 2011). Our results provide vital information about the dispersal patterns of a vector species that has put thousands of people at risk of infection with Tryp.…”

“…; Sloop et al . ). Our results provide vital information about the dispersal patterns of a vector species that has put thousands of people at risk of infection with Tryp.…”

Movement, impacts and management of plant distributions in response to climate change: insights from invasions

“…by hybridization, Lavergne and Molofsky 2007), especially when small isolated founder populations undergo rapid divergent evolution. Many cases of hybridization between related species that used to be geographically separated have been documented through invasion studies (Sloop et al 2011, Ward et al 2012), and can give insights into the likelihood of similar trajectories when species move in response to climate change.…”

Hybrid Typha×glauca outperforms native T. latifolia under contrasting water depths in a common garden

“…If these hybrids are competitively dominant, displacement of native lineages can occur. For example, hybridization has been linked to the displacement of native Spartina foliosa from San Francisco Bay (Sloop, Ayres & Strong 2010;Ayres, Zaremba, & Strong 2004) and the displacement of Typha latifolia and Typha angustifolia from sites in the Great Lakes region of North America (Shih & Finkelstein 2008;Travis, Marburger, Windels, & Kubátová, 2010;. In the case of Typha, three species co-occur in eastern North America: T. latifolia, thought to be native (Grace & Harrison 1986); T. angustifolia, which dispersed relatively recently between North America and Europe, and most likely originated in Europe, possibly with early European settlers (Ciotir, Kirk, Row, & Freeland, 2013), and their hybrid, T. × glauca (Galatowitsch, Anderson, & Ascher, 1999).…”