Reproductive biology, ecological life history/demography and genetic diversity of the megagenus Astragalus (Fabaceae, Papilionoideae)

Abstract

Astragalus is the largest genus of seed plants; however, information on its reproductive biology and life history is widely scattered in the literature. About 96% of the species are perennials and 4% annuals; many are rare endemics. Astragalus species are obligate or facultative outcrossers, and inbreeding depression is higher in self-compatible (SC) than in self-incompatible (SI) species. The most frequent pollinators are Bombus, Osmia and Anthophora. On average, 48% of ovules produce seeds, and 40% of flowers produce fruits. Seed/ovule and fruit/flower ratios are lower in SC than in SI species. Predispersal insect seed predation ranges from 0 to 93%, and major predators are Acanthoscelides, Bruchophagus and Tychius. Seeds have physical dormancy and typically form a seed bank. C 3 is the only photosynthetic pathway in the genus. Population growth may be cyclic or noncyclic, and genetic diversity of a taxon may or may not be related to size of geographic range.

Variations in Structure among Androecia and Floral Nectaries in the Inverted Repeat-Lacking Clade (Leguminosae: Papilionoideae)

“…All four types of androecium are found in the IRLC, sometimes coexisting in one genus. For example, most members of the world’s largest angiosperm ‘megagenus’, Astragalus , possess diadelphous androecia [ 7 ]. However, monadelphous androecia have been reported in several species, such as A. monadelphus Maxim., A. neomonadelphus H.T.Tsai & T.F.Yu, and A. donianus DC.…”

Reproductive Ecology and Bee Associates of Packard's Milkvetch (Astragalus packardiae), a Rare Plant Endemic to Southwestern Idaho

“…Indeed, previous Astragalus studies establish bees as common floral visitors (Green and Bohart 1975, Karron 1987, Kaye 1999, Clement et al 2006, Watrous and Cane 2011, Soltani et al 2021). Five populations with several subpopulations of Packard's milkvetch have been discovered, primarily on lands managed by the Bureau of Land Management, but a few subpopulations occur on state and private lands.…”

“…Descriptive natural history studies are an asset in identifying limiting life history stages in rare plant species (Schemske et al 1994), yet many life history traits of Packard's milkvetch, such as the breeding and mating system, are largely unknown. While Astragalus is the largest flowering plant genus with >2300 species worldwide and at least 156 species in the Intermountain West (Cronquist et al 1989, Soltani et al 2021), the breeding biology of <1% of all Astragalus species is known (Watrous and Cane 2011, Soltani et al 2021). The breeding systems of Astragalus can be quite variable, from self-fertilizing to complete outcrossing; therefore, reliably predicting the breeding system of any given Astragalus species is difficult (Watrous and Cane 2011, Soltani et al 2021).…”

Linking pollen limitation and seed dispersal effectiveness

“…This negative effect of PL is observed in most Angiosperms investigated so far (see Burns et al., 2019; García‐Camacho & Totland, 2009; Wolowski et al., 2014). The negative effects of human activities on pollinators worldwide are expected to progressively exacerbate PL (González‐Varo et al., 2013; Neuschulz et al., 2016), raising concerns about the immediate and delayed impacts of PL on reproductive success and population dynamics of plant species (Burns et al., 2019; Knight et al., 2005; Soltani et al., 2021).…”