CR2025_48 The mystery of widespread endemics: why do some species spread while others don’t?

Lead Supervisor: Alastair Culham, Department of Ecology and Evolutionary Biology, University of Reading

Email: a.culham@reading.ac.uk

Co-supervisors: Chris Yesson, Zoological Society of London; Kalman Konyves, Royal Horticultural Society

The Mediterranean is one of the world’s biodiversity hotspots and has a high degree of endemism.  This hyperdiversity has led to much conservation attention being lavished on rare, narrowly distributed species. Ecological approaches to species diversity measures and conservation priority accept that species have core and satellite areas (1). However, it is entirely possible that this apparent pattern of taxonomic rarities simply reflects the genetic and ecological edges of much commoner and more widespread species and be an artefact of the inconsistent application of species concepts.  In this study we aim to root the understanding of narrowly endemic species by detailed population level study of their widespread congeners.  We have developed expertise in the phylogeny of the Hyacinthineae tribe in Asparagaceae which includes a number of genera showing this pattern of widespread species linked to narrow endemics. The recent publication of a library of nuclear gene baits for the Asparagaceae (2) now gives us access to DNA sequence data that will be useful at the population level and opens, for the first time, the chance to develop phylogenetic trees to study this phenomenon. This project proposes to explore the genetic, ecological and climatic variation across the range of two widespread species of Hyacinthineae, Prospero autumnalis and Muscari comosum (Figure 1) and their close and narrowly distributed relatives.  Each of the two species has more than 10 closely related species that have narrow distributions.

We will sample each of these species complexes across their geographic range, dividing widespread taxa into geographic units treated as equivalent to the endemic species.  The resulting dataset will allow the exploration of genetic differentiation across within-species geographic groups and compare these with narrow endemics, in turn linking edaphic and biotic differentiation to specific vegetation types, soils and climates.  The study is key to the understanding of how speciation happens in plants, and the degree to which morphospecies, ecospecies and genetic lineages overlap and the degree to which humans have a tendency to recognise edges of continuous variation as distinct taxa.

We already hold living and preserved plant collections of both plant groups and expect to supplement these with targeted fieldwork to fill sampling gaps.  For each species complex we will sample comprehensively across the geographic range aiming for a minimum of 90 samples per complex.  Using a combination of enriched nuclear DNA markers and genome skim data the project will build comprehensive multi-genome phylogenetic trees and networks to track the pattern of genetic relatedness.  These data will be matched to analysis of the climate envelope, ecology and populational data, including numbers of seed set, organism size etc.  Overlaid on this will be the generation of regional phenological datasets through data mining of iNaturalist (3) and herbarium collections (4) and mapping of geographic distribution and frequency.  Such rich data from numerous sources are now available through the combined sources of digital herbaria, online recording apps, fine scale climate and soil maps and unparalleled access to next generation sequencing.  Using the University cluster computing facility we have the capacity to process these data.

This is the first study of mediterranean geophytes at such a detailed level and offers the opportunity to advance the fundamental understanding of biodiversity in the Mediterranean basin and beyond.

Training opportunities: 

The student has the opportunity to join an established research team at the University of Reading to learn approaches to genomics and molecular analysis, to develop an understanding of perceived patterns of biodiversity.  There will be opportunities to conduct fieldwork with experienced botanists.  Through collaboration with Zoological Society of London, the student will gain insights into the charity funded conservation sector and have opportunity to link with researchers there.  The collaboration with the Royal Horticultural Society gives unrivalled opportunity to link to the specialist horticulture sector including access to one of the largest living plant collections in the U.K. 

Student profile:

You will have a degree in biology or a related discipline, confidence in computational biology and enthusiasm for fieldwork.  You will need good organisational skills, a thirst to develop new knowledge and the ability and willingness to work as part of a team.  

Co-Sponsorship details: 

This project will receive a CASE award from Royal Horticultural Society.

References:

• Burgess, M.D., Eaton, M.A. and Gregory, R.D., 2020. A review of spatial patterns across species ranges to aid the targeting of conservation interventions. Biological Conservation, 251, p.108755.
• Bentz, P.C. and Leebens‐Mack, J., 2024. Developing Asparagaceae1726: An Asparagaceae‐specific probe set targeting 1726 loci for Hyb‐Seq and phylogenomics in the family. Applications in Plant Sciences, p.e11597.
• Wolf, S., Mahecha, M.D., Sabatini, F.M., Wirth, C., Bruelheide, H., Kattge, J., Moreno Martínez, Á., Mora, K. and Kattenborn, T., 2022. Citizen science plant observations encode global trait patterns. Nature Ecology & Evolution, 6(12), pp.1850-1859.
• Gaier, A.G. and Resasco, J., 2023. Does adding community science observations to museum records improve distribution modeling of a rare endemic plant?. Ecosphere, 14(3), p.e4419.