Hybridization dynamics of invasive cattail (Typhaceae) stands in the Western Great Lakes Region of North America: a molecular analysis

Abstract

Summary1. By increasing vigour and broadening ecological tolerances, hybridization between native and introduced species may serve as a primary driver of invasiveness. 2. Cattails (Typha, Typhaceae) are clonal wetland graminoids that are known to hybridize where anthropogenic influences have resulted in distributional overlap. 3. In order to gauge the relative performance of hybrid vs. pure Typha, we characterized hybridization and clonal growth where native Typha latifolia and introduced Typha angustifolia occur together in the Western Great Lakes Region of North America. 4. Based on microsatellite markers, we documented F 1 hybrids as the most common class at five intensively sampled sites, constituting up to 90% of the genets and 99% of the ramets. Backcrosses to one or the other parent constituted 5-38% of the genets. Pure T. latifolia was rare and never constituted more than 12% of the genets. 5. F 1 hybrid genets achieved the highest mean ramet numbers at three sites, and were second in size only to T. angustifolia at two sites; however, these differences were not significant based on sitespecific one-way anovas. 6. F 1 hybrids exhibited little height advantage over other Typha classes, although there was a general tendency for hybrids in relatively mixed stands to be among the tallest genets in shallow water, but among the shortest genets in deeper water. 7. Native T. latifolia was found growing at the shallowest water depths at the only site where it was sufficiently abundant to be included in statistical comparisons. 8. Synthesis. The role of hybridization in plant invasions can be difficult to confirm in the absence of molecular data, particularly for clonal species where the boundaries separating individuals are otherwise difficult to discern. Here, we used molecular markers to document the prevalence and performance of hybrid genets in five invasive Typha stands covering a broad area of the Western Great Lakes Region. We found an extremely high prevalence of F 1 hybrids within mixed Typha stands. This, coupled with the typically larger sizes of hybrid genets, suggests that hybrids are capable of outperforming other Typha spp. and that hybridization has played an influential role in the North American cattail invasion.

Restoring diversity after cattail expansion: disturbance, resilience, and seasonality in a tropical dry wetland

“…The rapid expansion of cattail (Typha spp. ; Typhaceae) into wetlands historically not dominated by cattail has occurred across the globe in response to various natural and anthropogenic perturbations (e.g., nutrient enrichment, altered hydroperiod, reduced salinity, altered sedimentation rates, non-native genotype introductions) (Galatowitsch et al 1999, Zedler and Kercher 2004, Richardson 2008a, Travis et al 2010). Many of these cattail expansions have occurred fast enough and at a large enough scale to be called regime shifts (see Gunderson 2001, Hagerthey et al 2008.…”

Typha glauca Godron and its parental plants in Poland: taxonomic characteristics

“…The results of Snow et al (2010) also confirmed that hybrid populations can include substantial numbers of backcrossed genotypes. Most recently, studies by Kirk et al (2011) imply that the Typha glauca hybrid is not universally sterile, as suggested by Smith (1987), and that the levels of putative backcrossing found in their study exceed those discovered by Travis et al (2010) in the western Great Lakes region, which suggests that levels of backcrossing may be non-uniform across different areas of the Great Lakes. Backcrossing can lead to a reshuffling of parental genes; this can, in turn, allow hybrids to express environmental tolerances and growth characteristics that exceed those found in parental species.…”

“…The hybrid Typha glauca is common in many regions where the two parental species are sympatric (Galatowitsch et al, 1999;Travis et al, 2010;Kirk et al, 2011), although hybridization is not ubiquitous: in some areas of sympatry, no hybrids have been detected (Selbo & Snow, 2004;Tsyusko et al, 2005), and where they do occur, the frequency of hybrids can vary considerably between regions (Kirk et al, 2011). Some authors claim that the divergence of flowering time may be a critical barrier to species hybridization (Lamont et al, 2003).…”

“…Moreover, the going assumption until recently was that Typha glauca occurred only as F 1 progeny of T. latifolia and T. angustifolia as F 1 hybrids were considered to be almost universally sterile (Marsh, 1962;Smith, 1987Smith, , 2000. Travis et al (2010) showed that backcrosses do exist in natural populations. The results of Snow et al (2010) also confirmed that hybrid populations can include substantial numbers of backcrossed genotypes.…”

Role of molecular genetics in identifying ‘fine tuned’ natural enemies of the invasive Brazilian peppertree, Schinus terebinthifolius: a review

“…The benefits of hybridization such as heterosis or the production of novel genotypes may then outweigh the cost of losing gene combinations for local adaptation in the former native range (Verhoeven et al 2011). There are now a number of examples of inter-and intra-specific hybridization that have led to invasiveness (Schierenbeck and Ellstrand 2009;Gaskin et al 2009;Travis et al 2010;Mukherjee et al, pers. comm.…”