Rapid recent radiation of S-RNase lineages in Witheringia solanacea (Solanaceae)

Kostyun

2010

Heredity

The transition from self-incompatibility to self-compatibility is a common transition in angiosperms often reported in populations at the edge of species range limits. Geographically distinct populations of wild tomato species (Solanum section Lycopersicon (Solanaceae)) have been described as polymorphic for mating system with both self-incompatible and self-compatible populations. Using controlled pollinations and sequencing of the S-RNase mating system gene, we test the compatibility status of a population of S. peruvianum located near its southern range limit. Pollinations among plants of known genotypes revealed strong selfincompatibility; fruit set following compatible pollinations was significantly higher than following incompatible pollinations for all tested individuals. Sequencing of the S-RNase gene in parents and progeny arrays was also as predicted under self-incompatibility. Molecular variation at the S-RNase locus revealed a diverse set of alleles, and heterozygosity in over 500 genotyped individuals. We used controlled crosses to test the specificity of sequences recovered in this study; in all cases, results were consistent with a unique allelic specificity for each tested sequence, including two alleles sharing 92% amino-acid similarity. Site-specific patterns of selection at the S-RNase gene indicate positive selection in regions of the gene associated with allelic specificity determination and purifying selection in previously characterized conserved regions. Further, there is broad convergence between the present and previous studies in specific amino-acid positions inferred to be evolving under positive selection.

Section: Js Miller and Jl Kostyunmentioning

confidence: 74%

Functional gametophytic self-incompatibility in a peripheral population of Solanum peruvianum (Solanaceae)

Kostyun

2010

Heredity

“…GSI is well studied in Solanaceae and has been characterized for natural populations of species from several genera (eg, Lycium, Richman, 2000;Petunia, Wang et al, 2001; Physalis, Kohn, 1999;Solanum, Richman et al, 1995;Witheringia, Richman andKohn, 2000, Stone andPierce, 2005). Data from these species generally meet expectations; individuals are heterozygous and populations are highly polymorphic at the S-RNase locus (see reviews by Lawrence, 2000;Castric and Vekemans, 2004).…”

Section: Introductionmentioning

confidence: 86%

“…Despite equal numbers of TS lineages between two species of Witheringia, estimates of S-RNase diversity were over twice as high for W. solanacea compared to W. maculata (Stone and Pierce, 2005). Similarly, Richman and Kohn's (1999) comparison of Physalis cinerascens and Physalis crassifolia, showed variation in allele number but not allelic age, as measured by the number of TG lineages.…”

Section: Introductionmentioning

confidence: 99%

“…We measured terminal branch lengths in L. parishii to facilitate comparisons with previous studies in Lycium (Richman and Kohn, 2000) and Solanaceae (Richman and Kohn, 2000;Stone and Pierce, 2005). After verifying that the L. parishii sequences did not significantly deviate from clocklike behavior using a two-cluster test in LINTREE (Takezaki et al, 1995), terminal branch lengths were measured using KITSCH (Felsenstein, 2005).…”

Section: Parishii S-rnase Diversitymentioning

confidence: 99%

“…These authors suggest that a major determinant of allele number in populations is a result of differences among species in lifehistory characteristics that affect both population size and longevity. Several studies have considered the relationship between S-RNase diversity and life-history characteristics (Richman andKohn, 1999, 2000;Lu, 2001;Stone and Pierce, 2005); however, no clear association has emerged in Solanaceae. Further sampling of species closely related to those previously studied can strengthen overall patterns of TG evolution in Solanaceae and highlight differences between congeners.…”

Section: Introductionmentioning

confidence: 99%

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Gametophytic self-incompatibility in Lycium parishii (Solanaceae): allelic diversity, genealogical structure, and patterns of molecular evolution at the S-RNase locus

Savage

2006

Heredity

We characterized allelic diversity at the locus controlling selfincompatibility (SI) for a population of Lycium parishii (Solanaceae) from Organ Pipe National Monument, Arizona. Twenty-four partial sequences of S-RNase alleles were recovered from 25 individuals. Estimates of allelic diversity range from 23 to 27 alleles and, consistent with expectations for SI, individuals are heterozygous. We compare S-RNase diversity, patterns of molecular evolution, and the genealogical structure of alleles from L. parishii to a previously studied population of its congener L. andersonii. Gametophytic SI is well characterized for Solanaceae and although balancing selection is hypothesized to be responsible for high levels of allelic divergence, the pattern of selection varies depending on the portion of the gene considered. Site-specific models investigating patterns of selection for L. parishii and L. andersonii indicate that positive selection occurs in those regions of the S-RNase gene hypothesized as important to the recognition response, whereas positive selection was not detected for any position within regions previously characterized as conserved. A 10-species genealogy including S-RNases from a pair of congeners from each of five genera in Solanaceae reveals extensive transgeneric evolution of L. parishii S-RNases. Further, within Lycium, the D n /D s ratios for pairs of closely related alleles for intraspecific versus interspecific comparisons were not significantly different, suggesting that the S-RNase diversity recovered in these two species was present prior to the speciation event separating them. Despite this, two S-RNases from L. parishii are identical to two previously reported alleles for L. andersonii, suggesting gene flow between these species.

Colonization, Baker's law, and the evolution of gynodioecy in Hawaii: implications from a study of Lycium carolinianum

Blank

Levin

2019

American J of Botany

Premise As Baker’s law suggests, the successful colonization of oceanic islands is often associated with uniparental reproduction (self‐fertility), but the high incidence of dimorphism (dioecy, gynodioecy) on islands complicates this idea. Lycium carolinianum is widespread, occurring on the North American mainland and the Hawaiian Islands. We examined Baker's ideas for mainland and island populations of L. carolinianum and examined inbreeding depression as a possible contributor to the evolution of gynodioecy on Maui. Methods Controlled crosses were conducted in two mainland populations and two populations in Hawaii. Treatments included self and cross pollination, unmanipulated controls, and autogamy/agamospermy. Alleles from the self‐incompatibility S‐RNase gene were isolated and compared between mainland and island populations. Given self‐compatibility in Hawaii, we germinated seeds from self‐ and cross‐ treatments and estimated inbreeding depression using seven traits and a measure of cumulative fitness. Results Mainland populations of Lycium carolinianum are predominately self‐incompatible with some polymorphism for self‐fertility, whereas Hawaiian populations are self‐compatible. Concordantly, S‐RNase allelic diversity is reduced in Hawaii compared to the mainland. Hawaiian populations also exhibit significant inbreeding depression. Conclusions Self‐compatibility in Hawaii and individual variation in self‐fertility in mainland populations suggests that a colonization filter promoting uniparental reproduction may be acting in this system. Comparison of S‐RNase variation suggests a collapse of allelic diversity and heterozygosity at the S‐RNase locus in Hawaii, which likely contributed to mate limitation upon arrival to the Pacific. Inbreeding depression coupled with autonomous self‐fertilization may have led to the evolution of gynodioecy on Maui.