Predispersal seed predation is higher in a rare species than in its widespread sympatric congeners (<i>Astragalus</i>, Fabaceae)

Combs, Julie K.; Lambert, Amy M.; Reichard, Sarah

doi:10.3732/ajb.1300238

Cited by 27 publications

(37 citation statements)

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“…Just as pollen limitation commonly constrains seed production, so too does pre-dispersal seed predation (Brody, 1991;Ehrlén, Käck, & Ågren, 2002;Leimu, Syrjanen, Ehrlén, & Lehtila, 2002;Louda, 1982;Weppler & Stoecklin, 2006). Perhaps due to their relatively large seeds, Astragalus species often suffer substantial pre-dispersal seed loss to insects, ranging from roughly 5% to 78% (Boe & Johnson, 2008;Combs, Lambert, & Reichard, 2013;Combs, Reichard, Groom, Wilderman, & Camp, 2011;Green, 1976;Jordano, Haeger, & Rodriguez, 1990;Kaye, 1999;Lesica, 1995;Platt, Hill, & Clark, 1974). In keeping with a prior observational study of A. utahensis (Green, 1976), we found that pre-dispersal seed predation strongly impacted seed production in this species.…”

Section: That Visitmentioning

confidence: 99%

Pre‐dispersal seed predation and pollen limitation constrain population growth across the geographic distribution of Astragalus utahensis

Baer

Maron

2018

Journal of Ecology

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A central focus of ecology is to understand the conditions under which biotic interactions affect species’ abundance and distribution. Classic and recent studies have shown that biotic interactions can strongly impact local or regional patterns of species abundance, but two fundamental questions remain largely unaddressed for non‐competitive biotic interactions. First, do the effects of these interactions on population performance change predictably with environmental context? Second, to what extent do population‐scale effects contribute to limiting species’ geographic distributions? To address these questions, we experimentally assessed the extent to which pollen limitation and insect seed predators affected the fecundity and projected population growth rate (λ) of the native forb Astragalus utahensis. We studied populations at the centre and northern edge of the latitudinal range of A. utahensis that occur across a gradient in abiotic harshness characterized primarily by declining mean annual precipitation. Supplementing pollen and suppressing pre‐dispersal seed predators increased seed production similarly within A. utahensis populations at the centre and northern edge of the range. Integral projection population models revealed that relaxing these checks on seed production tended to increase λ in most populations, regardless of their location within the range. Synthesis. Our results suggest that pollen limitation and insect herbivores limit population growth in A. utahensis similarly across the centre‐to‐north portion of its latitudinal distribution. However, because A. utahensis population growth barely reaches the level of replacement at the northern range edge, the reduction in λ resulting from these interactions may contribute to limiting expansion at the northern edge of A. utahensis’ latitudinal range.

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Section: That Visitmentioning

confidence: 99%

Pre‐dispersal seed predation and pollen limitation constrain population growth across the geographic distribution of Astragalus utahensis

Baer

Maron

2018

Journal of Ecology

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“…Nevertheless, we presently lack the data to assess this prediction. These should be research priorities for the near future, as we know remarkably little about the phylogenetic distribution of traits related to chronic rarity (Kunin & Gaston 1993;Ancheta & Heard 2011;Combs et al 2013), much less the distribution of chronic rarity across the major physical realms of life, especially in highly diverse communities where there must be many rare species.…”

Section: Introductionmentioning

confidence: 99%

Rarity and persistence

Vermeij

Grosberg

2017

Ecology Letters

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Rarity is a population characteristic that is usually associated with a high risk of extinction. We argue here, however, that chronically rare species (those with low population densities over many generations across their entire ranges) may have individual-level traits that make populations more resistant to extinction. The major obstacle to persistence at low density is successful fertilisation (union between egg and sperm), and chronically rare species are more likely to survive when (1) fertilisation occurs inside or close to an adult, (2) mate choice involves long-distance signals, (3) adults or their surrogate gamete dispersers are highly mobile, or (4) the two sexes are combined in a single individual. In contrast, external fertilisation and wind-or water-driven passive dispersal of gametes, or sluggish or sedentary adult life habits in the absence of gamete vectors, appear to be incompatible with sustained rarity. We suggest that the documented increase in frequency of these traits among marine genera over geological time could explain observed secular decreases in rates of background extinction. Unanswered questions remain about how common chronic rarity actually is, which traits are consistently associated with chronic rarity, and how chronically rare species are distributed among taxa, and among the world's ecosystems and regions.

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“…The use of demographic comparisons of related rare and common taxa is an established method for examining factors regulating rare plant populations (Karron, 1987;Walck et al, 1999). This method has been used to compare functional traits (Hand et al, 2017), seed production and germination (Brown et al, 2003), reproductive and ecophysiological attributes (Osunkoya and Swanborough, 2001), responses to herbivory and invasive species removal (Leege et al, 2010), predispersal seed predation (Combs et al, 2011(Combs et al, , 2013, and the effects of invasive competitors (Combs et al, 2011) for rare and common taxa. In these studies, many of which compare endemic and widespread congeners, the noted demographic differences highlight the challenges that rare species face.…”

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confidence: 99%

“…Such a comparative framework can provide a better understanding of species characterized by narrow endemism, those that occur in one or a few populations and thus are confined to a single domain or a few localities (Kruckeberg and Rabinowitz, 1985). Furthermore, the use of a framework that examines rare-common differences in sympatric congeneric populations may be especially insightful because confounding factors such as differences in phylogeny, ecology, and local environmental factors can be controlled or reduced (Combs et al, 2013). Despite the applicability of this method, few studies have directly tested whether the process of seed dispersal differs for rare and common species (Pirie et al, 2000).…”

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Overall seed dispersal effectiveness is lower in endemic Trillium species than in their widespread congeners

Miller

Kwit

2018

American J of Botany

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Comparing ecological attributes of endemic species with related, widespread species can reveal differences accounting for rarity. Forests of the southeastern United States are home to many range-restricted endemic and widespread species of Trillium, a genus of ant-dispersed herbs. Evidence suggests that aspects of seed-related life history stages are often correlated with plant rarity, but few studies have tested whether the process of seed dispersal differs for endemic and widespread species. To address this question, we compared aspects of seed dispersal effectiveness (SDE) for three sympatric, widespread endemic Trillium species pairs. METHODS: We observed seed dispersal for Trillium species pairs by ants at eight sites, recorded numbers of seeds dispersed and dispersal distances, and described disperser interactions. To test disperser preference, we presented seeds of each pair to captive colonies of Aphaenogaster picea, a keystone disperser. Seeds were assigned scores based on worker behavior, and we recorded proportions of seeds dispersed after 1 h and 24 h. KEY RESULTS: Field observations yielded some significant within-pair differences. Ants dispersed more seeds of widespread species for all pairs, although dispersal distances did not differ. In laboratory experiments, after 24 h, ants dispersed more seeds of widespread species into nests. CONCLUSIONS: Endemic Trillium species had lower overall SDE than did their widespread congeners. These findings add to the list of ecological and demographic challenges that face endemic plants when compared to common congeners. Lower SDE may negatively impact reproductive rates and the colonization of new habitats, which may contribute to patterns of endemism.

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Predispersal seed predation is higher in a rare species than in its widespread sympatric congeners (Astragalus, Fabaceae)

Cited by 27 publications

References 50 publications

Pre‐dispersal seed predation and pollen limitation constrain population growth across the geographic distribution of Astragalus utahensis

Pre‐dispersal seed predation and pollen limitation constrain population growth across the geographic distribution of Astragalus utahensis

Rarity and persistence

Overall seed dispersal effectiveness is lower in endemic Trillium species than in their widespread congeners

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