Dataset Information

Gametophyte niche differences among sympatric tree ferns.

ABSTRACT: Forest community assembly is usually framed in terms of sporophyte dynamics; however, the recruitment and maintenance of fern populations, frequently influential in forest composition and structure, are initially determined by gametophytes. Sporophytes of three Cyathea tree fern species show habitat partitioning along gradients of phosphorus and light; we asked whether gametophyte niche differences parallel this pattern. To compare niche characteristics among taxa we compared growth rates to a size threshold (?3 mm) of gametophytes under controlled conditions using a multi-factorial, multi-level (3 × 4) experiment, varying irradiance (5.4 ± 4.4; 59.1 ± 44.3; 107 ± 74.1 µmol m-2 s-1) and orthophosphate concentrations (5, 10, 20, 40 mg kg-1). Gametophytes of the pioneer species C. medullaris developed to the size threshold across a broad range of phosphate and irradiance treatments (more than 20% of gametophytes in ? 7 of the 12 treatments), peaking at 20 mg kg-1 P and 60 µmol m-2 s-1 irradiance. The growth rates of the forest understorey species C. dealbata and C. smithii also peaked at 60 µmol m-2 s-1 but varied across treatments, suggesting niche differentiation along irradiance and orthophosphate gradients. Our analysis suggests that gametophyte development is strategically aligned to the ecological habits of sporophytes and that forest community assembly is likely strongly influenced by the independent gametophyte life-stage.

SUBMITTER: Brock JMR

PROVIDER: S-EPMC6371912 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Gametophyte niche differences among sympatric tree ferns.

Brock James M R JMR Burns Bruce R BR Perry George L W GLW Lee William G WG

Biology letters 20190101 1

Forest community assembly is usually framed in terms of sporophyte dynamics; however, the recruitment and maintenance of fern populations, frequently influential in forest composition and structure, are initially determined by gametophytes. Sporophytes of three Cyathea tree fern species show habitat partitioning along gradients of phosphorus and light; we asked whether gametophyte niche differences parallel this pattern. To compare niche characteristics among taxa we compared growth rates to a s ...[more]

PMID: 30958217

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Project description:Competition theory states that multiple species should not be able to occupy the same niche indefinitely. Morphologically, similar species are expected to be ecologically alike and exhibit little niche differentiation, which makes it difficult to explain the co-occurrence of cryptic species. Here, we investigated interspecific niche differentiation within a complex of cryptic bumblebee species that co-occur extensively in the United Kingdom. We compared the interspecific variation along different niche dimensions, to determine how they partition a niche to avoid competitive exclusion. We studied the species B. cryptarum, B. lucorum, and B. magnus at a single location in the northwest of Scotland throughout the flight season. Using mitochondrial DNA for species identification, we investigated differences in phenology, response to weather variables and forage use. We also estimated niche region and niche overlap between different castes of the three species. Our results show varying levels of niche partitioning between the bumblebee species along three niche dimensions. The species had contrasting phenologies: The phenology of B. magnus was delayed relative to the other two species, while B. cryptarum had a relatively extended phenology, with workers and males more common than B. lucorum early and late in the season. We found divergent thermal specialisation: In contrast to B. cryptarum and B. magnus, B. lucorum worker activity was skewed toward warmer, sunnier conditions, leading to interspecific temporal variation. Furthermore, the three species differentially exploited the available forage plants: In particular, unlike the other two species, B. magnus fed predominantly on species of heather. The results suggest that ecological divergence in different niche dimensions and spatio-temporal heterogeneity in the environment may contribute to the persistence of cryptic species in sympatry. Furthermore, our study suggests that cryptic species provide distinct and unique ecosystem services, demonstrating that morphological similarity does not necessarily equate to ecological equivalence.

Project description:AIM:Scaly tree ferns, Cyatheaceae, are a well-supported group of mostly tree-forming ferns found throughout the tropics, the subtropics and the south-temperate zone. Fossil evidence shows that the lineage originated in the Late Jurassic period. We reconstructed large-scale historical biogeographical patterns of Cyatheaceae and tested the hypothesis that some of the observed distribution patterns are in fact compatible, in time and space, with a vicariance scenario related to the break-up of Gondwana. LOCATION:Tropics, subtropics and south-temperate areas of the world. METHODS:The historical biogeography of Cyatheaceae was analysed in a maximum likelihood framework using Lagrange. The 78 ingroup taxa are representative of the geographical distribution of the entire family. The phylogenies that served as a basis for the analyses were obtained by Bayesian inference analyses of mainly previously published DNA sequence data using MrBayes. Lineage divergence dates were estimated in a Bayesian Markov chain Monte Carlo framework using beast. RESULTS:Cyatheaceae originated in the Late Jurassic in either South America or Australasia. Following a range expansion, the ancestral distribution of the marginate-scaled clade included both these areas, whereas Sphaeropteris is reconstructed as having its origin only in Australasia. Within the marginate-scaled clade, reconstructions of early divergences are hampered by the unresolved relationships among the Alsophila, Cyathea and Gymnosphaera lineages. Nevertheless, it is clear that the occurrence of the Cyathea and Sphaeropteris lineages in South America may be related to vicariance, whereas transoceanic dispersal needs to be inferred for the range shifts seen in Alsophila and Gymnosphaera. MAIN CONCLUSIONS:The evolutionary history of Cyatheaceae involves both Gondwanan vicariance scenarios as well as long-distance dispersal events. The number of transoceanic dispersals reconstructed for the family is rather few when compared with other fern lineages. We suggest that a causal relationship between reproductive mode (outcrossing) and dispersal limitations is the most plausible explanation for the pattern observed.

Dataset Information

Gametophyte niche differences among sympatric tree ferns.

Publications

Gametophyte niche differences among sympatric tree ferns.

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