Levels of allozyme diversity in closely related toadflaxes (Linaria, Plantaginaceae) and their correspondence with the breeding systems of the species

Abstract

Toadflaxes (Linaria Miller) represent the largest genus of the tribe Antirrhineae (formerly included in the Scrophulariaceae) of the Plantaginaceae family. These taxa vary according to their ranges (narrow-regional-widespread), biological traits (duration, flower morphology, breeding system) and ecological preferences. No comparative genetic studies have been performed up to the moment and the levels and distribution of genetic diversity within this genus remain undocumented. We have conducted an allozyme study in 8 taxa of Section Supinae. Five of them are narrow endemic, self-incompatible, insect-pollinated outcrossers that inhabit relatively unaltered habitats. The other three taxa are widespread, smallflowered selfers that inhabit crops subjected to high levels of recurrent disturbance. Linaria taxa showed moderate to high levels of genetic diversity. Parameters of genetic diversity were directly addressed to differences in breeding systems. Mean number of alleles per locus, total genetic diversity and genetic diversity within populations were higher among the outcrossers than among the selfers, (A e = 2.28 vs. 1.23; H T = 0.24 vs. 0.13; H S = 93.99% vs. 54.2%) while genetic diversity among populations and population differentiation were lower for the outcrossers than for the selfers (D ST = 0.02% vs. 45.98%; G ST = 0.03 vs. 0.52). Gene flow within and among populations produced a higher number of different genotypes (mean N G = 16 for outcrossers vs. 5.4 for selfers) and migrants (mean N m = 4.58 for outcrossers vs. 0.84 for selfers) that were attributed to an effective pollinator service in outcrossing populations. Differences in the levels and distribution of the genetic diversity are discussed in relation to biological and autoecological constraints of each group of taxa.

Autecological traits determined two evolutionary strategies in Mediterranean plants during the Quaternary: low differentiation and range expansion versus geographical speciation in Linaria

“…In our analyses, contrasting diversification rates are explained by unequal speciation rates, which are higher for xenogamous species (Table ). This result contrasts with recent research indicating that selfing may promote between‐population differentiation (Hamrick & Godt ; Charlesworth & Pannell ; see also Segarra‐Moragues & Mateu‐Andres for an example with some Linaria species) and speciation (Wendt et al . ; Martin & Willis ; Guo et al .…”

Macroevolutionary dynamics of nectar spurs, a key evolutionary innovation

“…S8). For example, some of the shortest spurs in Linaria are found in species with tiny corollas that appear to have evolved as a result of self‐fertilization (Segarra‐Moragues & Mateu‐Andrés, ; Blanco‐Pastor & Vargas, ). After accounting for corolla size, evolution of the spur : corolla ratio also displays a pattern of recurrent changes with relatively homogeneous rates (Figs S9, S10), and model testing supports a nonphylogenetic model (Table ), indicating a high evolutionary lability.…”

Heterozygote excess in ancient populations of the critically endangeredDioon caputoi(Zamiaceae, Cycadales) from central Mexico

“…The long life cycle and obligate outcrossing mating system (dioecy) of D. caputoi may be contributing factors which explain the high levels of allozyme diversity found in this study. It has been found that in systems where selfing is completely prevented, through dioecy (Costich & Meagher, 1992; Oostermeijer & De Knegt, 2004) or self‐incompatibility (Segarra‐Moragues & Mateu‐Andrés, 2007), allozyme diversity is higher within than among populations.…”