Conservation of old individual trees and small populations is integral to maintain species' genetic diversity of a historically fragmented woody perennial

Nicole Bezemer, Siegfried L. Krauss, David G. Roberts, Stephen D. Hopper

Research output: Contribution to journalArticle

Abstract

Historically fragmented and specialized habitats such as granite outcrops are understudied globally unique hot spots of plant evolution. In contrast to predictions based on mainstream population genetic theory, some granite outcrop plants appear to have persisted as very small populations despite prolonged geographic and genetic isolation. Eucalyptus caesia Benth. is a long-lived lignotuberous tree endemic with a naturally fragmented distribution on granite outcrops in south-western Australia. To quantify population to landscape-level genetic structure, we employed microsatellite genotyping at 14 loci of all plants in 18 stands of E. caesia. Sampled stands were characterized by low levels of genetic diversity, small absolute population sizes, localized clonality and strong fine-scale genetic subdivision. There was no significant relationship between population size and levels of heterozygosity. At the landscape scale, high levels of population genetic differentiation were most pronounced among representatives of the two subspecies in E. caesia as originally circumscribed. Past genetic interconnection was evident between some geographic neighbours separated by up to 20 km. Paradoxically, other pairs of neighbouring stands as little as 7 km apart were genetically distinct. There was no consistent pattern of isolation by distance across the 280 km range of E. caesia. Low levels of gene flow, together with strong drift within stands, provide some explanation of the patterns of genetic differentiation we observed. Individual genet longevity via the ability to repeatedly resprout and expand from a lignotuber may enhance the persistence of some woody perennial endemic plants despite small population size, minimal genetic interconnection and low heterozygosity.

Original languageEnglish
Number of pages19
JournalMolecular Ecology
DOIs
Publication statusE-pub ahead of print - Jul 2019

Cite this

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title = "Conservation of old individual trees and small populations is integral to maintain species' genetic diversity of a historically fragmented woody perennial",
abstract = "Historically fragmented and specialized habitats such as granite outcrops are understudied globally unique hot spots of plant evolution. In contrast to predictions based on mainstream population genetic theory, some granite outcrop plants appear to have persisted as very small populations despite prolonged geographic and genetic isolation. Eucalyptus caesia Benth. is a long-lived lignotuberous tree endemic with a naturally fragmented distribution on granite outcrops in south-western Australia. To quantify population to landscape-level genetic structure, we employed microsatellite genotyping at 14 loci of all plants in 18 stands of E. caesia. Sampled stands were characterized by low levels of genetic diversity, small absolute population sizes, localized clonality and strong fine-scale genetic subdivision. There was no significant relationship between population size and levels of heterozygosity. At the landscape scale, high levels of population genetic differentiation were most pronounced among representatives of the two subspecies in E. caesia as originally circumscribed. Past genetic interconnection was evident between some geographic neighbours separated by up to 20 km. Paradoxically, other pairs of neighbouring stands as little as 7 km apart were genetically distinct. There was no consistent pattern of isolation by distance across the 280 km range of E. caesia. Low levels of gene flow, together with strong drift within stands, provide some explanation of the patterns of genetic differentiation we observed. Individual genet longevity via the ability to repeatedly resprout and expand from a lignotuber may enhance the persistence of some woody perennial endemic plants despite small population size, minimal genetic interconnection and low heterozygosity.",
keywords = "clonal reproduction, conservation, Eucalyptus caesia, genetic diversity, granite outcrops, historic fragmentation, small populations, woody perennial, RARE MALLEE EUCALYPT, GRANITE OUTCROPS, MATING SYSTEM, MICROSATELLITE MARKERS, INBREEDING DEPRESSION, ALCANTAREA-IMPERIALIS, PLANT-POPULATIONS, COMPLEX HYBRIDITY, COMPUTER-PROGRAM, CLONE SIZE",
author = "Nicole Bezemer and Krauss, {Siegfried L.} and Roberts, {David G.} and Hopper, {Stephen D.}",
year = "2019",
month = "7",
doi = "10.1111/mec.15164",
language = "English",
journal = "Molecular Ecology",
issn = "0962-1083",
publisher = "Blackwell",

}

TY - JOUR

T1 - Conservation of old individual trees and small populations is integral to maintain species' genetic diversity of a historically fragmented woody perennial

AU - Bezemer, Nicole

AU - Krauss, Siegfried L.

AU - Roberts, David G.

AU - Hopper, Stephen D.

PY - 2019/7

Y1 - 2019/7

N2 - Historically fragmented and specialized habitats such as granite outcrops are understudied globally unique hot spots of plant evolution. In contrast to predictions based on mainstream population genetic theory, some granite outcrop plants appear to have persisted as very small populations despite prolonged geographic and genetic isolation. Eucalyptus caesia Benth. is a long-lived lignotuberous tree endemic with a naturally fragmented distribution on granite outcrops in south-western Australia. To quantify population to landscape-level genetic structure, we employed microsatellite genotyping at 14 loci of all plants in 18 stands of E. caesia. Sampled stands were characterized by low levels of genetic diversity, small absolute population sizes, localized clonality and strong fine-scale genetic subdivision. There was no significant relationship between population size and levels of heterozygosity. At the landscape scale, high levels of population genetic differentiation were most pronounced among representatives of the two subspecies in E. caesia as originally circumscribed. Past genetic interconnection was evident between some geographic neighbours separated by up to 20 km. Paradoxically, other pairs of neighbouring stands as little as 7 km apart were genetically distinct. There was no consistent pattern of isolation by distance across the 280 km range of E. caesia. Low levels of gene flow, together with strong drift within stands, provide some explanation of the patterns of genetic differentiation we observed. Individual genet longevity via the ability to repeatedly resprout and expand from a lignotuber may enhance the persistence of some woody perennial endemic plants despite small population size, minimal genetic interconnection and low heterozygosity.

AB - Historically fragmented and specialized habitats such as granite outcrops are understudied globally unique hot spots of plant evolution. In contrast to predictions based on mainstream population genetic theory, some granite outcrop plants appear to have persisted as very small populations despite prolonged geographic and genetic isolation. Eucalyptus caesia Benth. is a long-lived lignotuberous tree endemic with a naturally fragmented distribution on granite outcrops in south-western Australia. To quantify population to landscape-level genetic structure, we employed microsatellite genotyping at 14 loci of all plants in 18 stands of E. caesia. Sampled stands were characterized by low levels of genetic diversity, small absolute population sizes, localized clonality and strong fine-scale genetic subdivision. There was no significant relationship between population size and levels of heterozygosity. At the landscape scale, high levels of population genetic differentiation were most pronounced among representatives of the two subspecies in E. caesia as originally circumscribed. Past genetic interconnection was evident between some geographic neighbours separated by up to 20 km. Paradoxically, other pairs of neighbouring stands as little as 7 km apart were genetically distinct. There was no consistent pattern of isolation by distance across the 280 km range of E. caesia. Low levels of gene flow, together with strong drift within stands, provide some explanation of the patterns of genetic differentiation we observed. Individual genet longevity via the ability to repeatedly resprout and expand from a lignotuber may enhance the persistence of some woody perennial endemic plants despite small population size, minimal genetic interconnection and low heterozygosity.

KW - clonal reproduction

KW - conservation

KW - Eucalyptus caesia

KW - genetic diversity

KW - granite outcrops

KW - historic fragmentation

KW - small populations

KW - woody perennial

KW - RARE MALLEE EUCALYPT

KW - GRANITE OUTCROPS

KW - MATING SYSTEM

KW - MICROSATELLITE MARKERS

KW - INBREEDING DEPRESSION

KW - ALCANTAREA-IMPERIALIS

KW - PLANT-POPULATIONS

KW - COMPLEX HYBRIDITY

KW - COMPUTER-PROGRAM

KW - CLONE SIZE

U2 - 10.1111/mec.15164

DO - 10.1111/mec.15164

M3 - Article

JO - Molecular Ecology

JF - Molecular Ecology

SN - 0962-1083

ER -