Biology subjects

Kauai, F.

Publications and source records attributed to Kauai, F..

4 recordsLinked to original sources

bioRxiv2025

Dispersal evolution as a driver of island biodiversity

Island biodiversity reflects a tension between isolation and connectivity. Dispersal lies at the heart of this paradox: it enables colonization and ecological opportunity, yet excessive gene flow can constrain divergence and speciation. We use a spatially explicit, individual-based model to ask how dispersal evolution influences speciation and long-term diversity. Across archipelagos, rare long-distance dispersal events trigger colonization and divergence, after which dispersal traits evolve along two trajectories: increasing or decreasing range. These outcomes correlate with island size and isolation. Structured landscapes stabilize species richness through low turnover, whereas continuous landscapes remain species-poor despite high diversification rates. Our results reveal that spatial structure and dispersal evolution jointly govern biodiversity, underscoring the need to integrate movement into theories of speciation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=146 SRC="FIGDIR/small/690991v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@17d93ddorg.highwire.dtl.DTLVardef@176c011org.highwire.dtl.DTLVardef@13bbeb1org.highwire.dtl.DTLVardef@1646b9d_HPS_FORMAT_FIGEXP M_FIG Visual abstract The paradox of dispersal. Although elevated dispersal levels increases the number of ecological opportunities for individuals, it also increases gene flow. These counteract each other in terms of speciation, resulting in a speciation tug-of-war. C_FIG

evolutionary biology↗

bioRxiv2025

Ecological opportunity and the onset of polyploid niche expansion waves

Polyploidy, the presence of more than two sets of chromosomes, has evolved many times across the tree of life, yet we still do not know why some polyploid lineages persist while most go extinct. The establishment of polyploid populations is often reported to be associated with harsh environmental conditions, and stress tolerance in particular, which have led to the widespread view that polyploidy-specific niche requirements are key to their persistence at ecological and evolutionary timescales. Here, we reevaluate this perspective through a classical mathematical model of polyploid establishment, for which we provide new analytical and numerical results, along with an empirical case study. We show that simple eco-evolutionary processes at the margins of diploid range-expansion waves, more specifically ecological drift and dispersal limitation, can be sufficient to allow polyploid populations to carve out their own space, without any a priori adaptive advantage over their diploid ancestors. Our modelling effort reveals three key insights. First, polyploids most readily gain a foothold at the low-density front of a diploid range expansion wave, where ecological drift is strongest. Second, limited dispersal accelerates spatial clustering of polyploid organisms through assortative mating. Third, once spatially segregated, diploid and polyploid populations experience different environments, so natural selection can drive niche divergence. We illustrate these interconnected principles by simulating the phylogeographic history of a well-documented autopolyploid complex of Neobatrachus Australian burrowing frogs. Altogether, our results provide a neutral baseline against which the ecological consequences of polyploidization can be readily detected and inferred within natural populations. Significance statementPolyploidy, having multiple copies of the entire set of chromosomes, underpins major innovations in both animals and plants and fuels biodiversity. Yet, why some polyploid lineages are successful while others fail remains unclear. Our study shows that simple eco-evolutionary forces, specifically ecological drift at the edge of an expanding range and limited dispersal, can enable polyploids to establish and become geographically separated from their diploid relatives, even without any inherent adaptive benefits. This spatial segregation then exposes each cytotype to distinct environments, setting the stage for natural selection to operate. Our neutral theoretical framework helps biologists disentangle when polyploidy itself drives adaptation and when success is just a matter of being in the right place at the right time.

evolutionary biology↗

bioRxiv2023

Interspecific transfer of genetic information through polyploid bridges

Many organisms have more than two sets of chromosomes, due to whole genome duplication (WGD), and are thus polyploid. Despite usually being an ephemeral state in the history of life, polyploidy is widely recognized as an important source of genetic novelty over macroevolutionary scales. More recently, polyploidy has also been shown to facilitate interspecific gene flow, circumventing reproductive barriers between their diploid ancestors. Yet, the implications of WGD-linked introgression on community-level evolutionary dynamics remain unknown. Here, we develop a model of cytotype dynamics within mixed-ploidy populations to demonstrate that polyploidy can in fact serve as a bridge for gene flow between diploid lineages, where introgression is fully or partially hampered by the species barrier. Polyploid bridges emerge in the presence of triploid organisms, which despite critically low levels of viability, can still allow the transfer of alleles between diploid states of independently evolving mixed-ploidy species. Notably, while marked genetic divergence prevents WGD-mediated interspecific gene flow, we show that increased recombination rates can offset these evolutionary constraints, which allows a more efficient sorting of alleles at higher-ploidy levels before introgression into diploid gene pools. Additionally, we derive an analytical approximation for the rate of gene flow at the tetraploid level necessary to supersede introgression between diploids with non-zero introgression rates, which is especially relevant for plant species complexes, where interspecific gene flow is ubiquitous. Altogether, our results illustrate the potential impact of polyploid bridges on evolutionary change within and between mixed-ploidy populations.

evolutionary biology↗

bioRxiv2023

A metabolic perspective on polyploid invasion and the emergence of life histories: insights from a mechanistic model

Whole genome duplication (WGD, polyploidization), the fusion of unreduced gametes, has been identified as a driver of genetic and phenotypic novelty. Unreduced gamete formation is common in a wide range of species, but surprisingly, few polyploidization events have shown to be ecologically successful. Positive density dependence, by minority cytotype exclusion, and niche shifts are currently considered the most important drivers behind ecological failure or success. Genome doubling also results in increased cell sizes and metabolic expenses which, on their own may be sufficient to drive polyploid establishment in stable environments where their simple ancestors thrive. We developed a mechanistic model, motivated by data from natural plant polyploid species, to test whether realistic changes in size and metabolic efficiency allow polyploids to coexist with, or even invade, their original diploid population. Central to the model is metabolic efficiency, a functional trait that determines how energy gained from size-dependent photosynthetic metabolism is allocated to basal metabolism, somatic growth and reproductive growth. Polyploid invasion was observed across a wide range of metabolic efficiency differences between polyploids and their ancestors. Higher metabolic efficiency facilitates polyploid invasion, but even with minor deficits, establishment was facilitated by recurrent formation in these settings of high competition for nutrients. Interestingly, a long-term coexistence with the diploid ancestor was found to be possible only within a narrow range of this parameter space. Perenniality of the plants did not qualitatively affect these insights. Feedbacks between size-dependent metabolism and allocation of gained energy generated eventually size and age differences, resulting in intra- and intercytotype competition for nutrients as the major force for population dynamics. We thus demonstrate that changes in metabolic efficiency on their own are sufficient to impose establishment, but these advantages do not need to be substantial.

ecology↗