The “sexy shrimp”
Coral reefs in all tropical oceans.
Specimens of
We found evidence for at least five cryptic lineages (9%–22%
Intra‐specific negative density dependence promotes species coexistence by regulating population sizes. Patterns consistent with such density dependence are frequently reported in diverse tropical tree communities. Empirical evidence demonstrating whether intra‐specific variation is related to these patterns, however, is lacking. The present study addresses this important knowledge gap by genotyping all individuals of a tropical tree in a long‐term forest dynamics plot in tropical China. We show that related individuals are often spatially clustered, but having closely related neighbours reduces the growth performance of focal trees. We infer from the evidence that dispersal limitation and negative density dependence are operating simultaneously to impact the spatial distributions of genotypes in a natural population. Furthermore, dispersal limitation decreases local intra‐specific genetic diversity and increases negative density dependence thereby promoting niche differences and species coexistence as predicted by theory.
more » « less- NSF-PAR ID:
- 10064034
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Ecology Letters
- Volume:
- 21
- Issue:
- 8
- ISSN:
- 1461-023X
- Page Range / eLocation ID:
- p. 1174-1181
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Aim Thor amboinensis is currently considered a single circumtropical species. However, the tropical oceans are partitioned by hard and soft barriers to dispersal, providing ample opportunity for allopatric speciation. Herein, we test the null hypothesis thatT. amboinensis is a single global species, reconstruct its global biogeographical history, and comment on population‐level patterns throughout the Tropical Western Atlantic.Location Methods Thor amboinensis were obtained through field collection and museum holdings. We used one mitochondrial (COI ) and two nuclear (NaK, enolase) gene fragments for global species delimitation and phylogenetic analyses (n = 83 individuals, 30 sample localities), while phylogeographical reconstruction in theTWA was based onCOI only (n = 303 individuals, 10 sample localities).Results COI pairwise sequence divergence): four in the Indo‐West Pacific and one in the Tropical Western Atlantic. Phylogenetic reconstruction revealed that endemic lineages from Japan and the South Central Pacific are more closely related to the Tropical Western Atlantic lineage than to a co‐occurring lineage that is widespread throughout the Indo‐West Pacific. Concatenated and species tree phylogenetic analyses differ in the placement of an endemic Red Sea lineage and suggest alternate dispersal pathways into the Atlantic. Phylogeographical reconstruction throughout the Tropical Western Atlantic reveals little genetic structure over more than 3,000 km.Main conclusions Thor amboinensis is a species complex that has undergone a series of allopatric speciation events and whose members are in secondary contact in the Indo‐West Pacific. Nuclear‐ and mitochondrial‐ gene phylogenies show evidence of introgression between lineages inferred to have been separated more than 20 Ma. Phylogenetic discordance between multi‐locus analyses suggest thatT. amboinensis originated in the Tethys sea and dispersed into the Atlantic and Indo‐West Pacific through the Tethys seaway or, alternatively, originated in the Indo‐West Pacific and dispersed into the Atlantic around South Africa. Population‐level patterns in the Caribbean indicate extensive gene flow across the region. -
Yavitt, Joseph B. (Ed.)Conspecific negative density dependence (CNDD) promotes tree species diversity by reducing recruitment near conspecific adults due to biotic feedbacks from herbivores, pathogens, or competitors. While this process is well-described in tropical forests, tests of temperate tree species range from strong positive to strong negative density dependence. To explain this, several studies have suggested that tree species traits may help predict the strength and direction of density dependence: for example, ectomycorrhizal-associated tree species typically exhibit either positive or weaker negative conspecific density dependence. More generally, the strength of density dependence may be predictably related to other species-specific ecological attributes such as shade tolerance, or the relative local abundance of a species. To test the strength of density dependence and whether it affects seedling community diversity in a temperate forest, we tracked the survival of seedlings of three ectomycorrhizal-associated species experimentally planted beneath conspecific and heterospecific adults on the Prospect Hill tract of the Harvard Forest, in Massachusetts, USA. Experimental seedling survival was always lower under conspecific adults, which increased seedling community diversity in one of six treatments. We compared these results to evidence of CNDD from observed sapling survival patterns of 28 species over approximately 8 years in an adjacent 35-ha forest plot. We tested whether species-specific estimates of CNDD were associated with mycorrhizal association, shade tolerance, and local abundance. We found evidence of significant, negative conspecific density dependence (CNDD) in 23 of 28 species, and positive conspecific density dependence in two species. Contrary to our expectations, ectomycorrhizal-associated species generally exhibited stronger (e.g., more negative) CNDD than arbuscular mycorrhizal-associated species. CNDD was also stronger in more shade-tolerant species but was not associated with local abundance. Conspecific adult trees often have a negative influence on seedling survival in temperate forests, particularly for tree species with certain traits. Here we found strong experimental and observational evidence that ectomycorrhizal-associating species consistently exhibit CNDD. Moreover, similarities in the relative strength of density dependence from experiments and observations of sapling mortality suggest a mechanistic link between negative effects of conspecific adults on seedling and sapling survival and local tree species distributions.more » « less
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Abstract Animal pollination is critical for maintaining the reproduction and genetic diversity of many plant species, especially those in tropical ecosystems. Despite the threat to pollination posed by tropical deforestation, it remains an understudied process. In particular, little is known about these dynamics in multi‐paternal, successional plant species whose fruits can contain substantial genetic diversity. Given the importance of successional plants in reforestation, quantifying the factors that impact their reproduction is essential for understanding plant gene flow in the context of global change. In this study, we investigated pollen‐mediated gene flow at the multi‐paternal fruit level to quantify how tropical pollinators navigate and mediate gene flow in altered forests. Utilizing microsatellite genotyping and paternity analyses, we revealed that distinct plant neighborhood and individual factors drive pollen dispersal at the intra‐fruit scale. Variance in pollen dispersal distances was greater for neighborhoods with higher conspecific density, indicating that density dependent reproductive patterns play a role at this scale. Additionally, both the diversity and evenness of sires mediated by a single pollinator were affected by the size of the mother tree, that is, larger mothers received pollen from a less diverse, less even pool of sires per fruit. Pollinator body size was not found to be a significant driver of pollen dispersal, indicating that both small‐ and large‐bodied pollinators were equally important pollen dispersers at this scale. By exploring patterns of variation at the intra‐fruit level, we show that conspecific density and tree size significantly impact multi‐paternal pollen‐mediated gene flow, reinforcing the importance of investigating intraspecific, intra‐individual variance in plant reproduction.
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