title: The relationship between genetic diversity and species diversity – impact of parallel processes in isolated plant populations
title: Der Zusammenhang zwischen genetischer- und Artendiversität – der Einfluss paralleler Prozesse in isolierten Pflanzenpopulationen
Creators: name: Hornemann, Gitte
Publisher: name: Philipps-Universität Marburg
Year: 2012
Subjects: Conservation
Orchids
Genetische Variabilität
Naturschutz
Orchideen
Drift
Biowissenschaften, Biologie
Populationsgenetik
Trockenrasen
Genetic diversity
Dry grasslands
Genfluss
Biodiversität
Artenreichtum
Biodiversity
Species diversity
Gene flow

description: Chapter 1: The relationship between
      genetic diversity (GD) and species diversity (SD) is still
      not clearly understood. By now, many theoretical and
      experimental studies on this essential issue of biodiversity
      research exist and different hypotheses have been developed
      that predict either positive or negative GD-SD correlations.
      Especially processes like drift and selection are believed to
      indirectly create positive GD-SD correlations by acting
      similarly and in parallel on both levels. In this study we
      analyze the impact of parallel processes on genetic diversity
      of eight dry grassland plant species in central Germany. We
      used amplified fragment length polymorphism (AFLP) to
      determine genetic diversity within species. In total 31
      isolated grassland patches differing in species richness
      (range: 43 to 126 dry grassland species per site) and habitat
      heterogeneity were studied. Drift and selection are expected
      to be strong determinants of GD and SD in this study system
      because of long term habitat isolation and restricted gene
      flow among populations and plant communities. We found high
      genetic diversity within populations throughout all study
      species. In three of the eight species we found a positive
      GD-SD correlation. However, effects of drift and selection
      are generally low within our study system and probably did
      not create the observed patterns. Although gene flow appears
      to be restricted in some cases, species specific responses to
      habitat isolation are strongly dependent on the species’ life
      history traits, such as breeding system and dispersal
      strategy. Single species studies may thus not be able to draw
      general conclusions about the processes acting in such study
      systems. Therefore, our study highlights the importance for
      multi species studies. Chapter 2: The conservation of
      endangered species critically depends on the understanding to
      which degree short-term fitness and long-term trends are
      affected by intrinsic local conditions and external global
      dynamics. However, studies combining long-term demographic
      data with population level analyses of site conditions, GD
      and reproduction as well as with climatic data are still
      rare. Here we studied the endangered orchid Anacamptis morio,
      representative for species with a sub-mediterranean
      distribution. For populations at the northern range edge, we
      combined long-term monitoring data (1977-2010) with climatic
      data and analyzed reproductive fitness components, GD and
      abiotic site conditions. Reproduction was generally low as
      expected from the deceptive pollination system, and was
      positively influenced by population size and xerothermic site
      quality. The majority of populations showed a positive
      population trend, which was paralleled by an increase in
      spring temperature and which was positively affected by site
      quality. High levels of GD were found in the populations
      which were at gene flow-drift equilibrium. A. morio may
      profit from increasing spring temperatures because of
      increased reproductive output. Nevertheless, whether climate
      change results in fitness increase may depend on the
      maintenance and provision of optimal site quality, i.e.
      xerothermic and nutrient poor conditions. Chapter 3: In plant
      populations a positive correlation between population size,
      genetic variation and fitness components is often found, due
      to increased pollen limitation or reduced genetic variation
      and inbreeding depression in smaller populations. However,
      components of fitness also depend on environmental factors
      which can vary strongly between years. The dry grassland
      species Muscari tenuiflorum experiences long term habitat
      isolation and small population sizes. We analyzed seed
      production of M. tenuiflorum in four years and its dependence
      on population size and genetic variation. Genetic diversity
      within populations was high (AFLP: HE = 0.245; allozymes: HE
      = 0.348). An analysis of molecular variance revealed
      considerable population differentiation (AFLP: 26 %;
      allozyme: 17 %). An overall pattern of isolation by distance
      was found, which, however was not present at distances below
      20 km indicating stronger effects of genetic drift. Genetic
      diversity was positively correlated to population size. Self
      pollination reduced seed set by 24 % indicating inbreeding
      depression. Reproductive fitness was not correlated to
      genetic diversity and a positive correlation with population
      size was present in two of four study years. The absence of a
      general pattern stresses the importance for multi-year
      studies. Overall the results show that despite long term
      habitat isolation M. tenuiflorum maintains seed production in
      many years independent of population size. The long term
      persistence of populations is thus expected to depend less on
      intrinsic genetic or demographic properties affecting seed
      production but on successful plant establishment and
      persistence which are based on conservation and protection of
      suitable habitat.
description: Das Ziel der vorliegenden Arbeit
      ist es, die Faktoren zu untersuchen, die die genetische
      Diversität und die Artenvielfalt in isolierten
      Trockenrasenarten beeinflussen. Ein besonderer Schwerpunkt
      lag in der Untersuchung einer möglichen Korrelation zwischen
      beiden Biodiversitätsebenen, die sich theoretisch unter den
      gegebenen Umweltbedingungen einstellen kann. Hierbei spielen
      parallele Prozesse (z. B. genetische Drift, Migration,
      Selektion), also Prozesse, die in ähnlicher Weise auf beide
      Ebenen wirken, eine maßgebliche Rolle. Der Ansatz viele Arten
      gleichzeitig zu untersuchen, erlaubt es die
      Verallgemeinbarkeit von parallelen Effekten auf die beiden
      Biodiversitätsebenen zu testen. Wir fanden begrenzte Hinweise
      auf eine positive Korrelation zwischen genetischer- und
      Artendiversität. Zusammenfassend lässt sich sagen, dass die
      Habitatisolation den Genfluss zwischen den Populationen schon
      auf sehr geringer räumlicher Skala begrenzt. Die genetische
      Resonanz darauf ist stark artabhängig und durch die
      jeweiligen biologischen Artmerkmale bestimmt. Die Mehrzahl
      der acht untersuchten Arten besitzt Eigenschaften, die sie
      weniger anfällig für genetische Verarmung durch
      Habitatisolation und kleine Populationsgröße machen. Dies
      betont die Bedeutung für Vielartenstudien, wenn
      Umwelteinflüsse auf Pflanzenpopulationen untersucht werden
      sollen. Die beiden Fallstudien in A. morio und M. tenuiflorum
      ergaben zusätzliche wertvolle Informationen über reproduktive
      Fitness und zeigten, dass Individuenzahlen und Reproduktion
      stark zwischen den Jahren variieren können. Darüber hinaus
      konnten wir einer der Versuchsarten zeigen, dass auch globale
      Veränderungen (Klimawandel) Pflanzenpopulationen beeinflussen
      können, indem sie auf das Blühverhalten wirken. Ob jedoch
      solche, auf den ersten Blick förderlichen Effekte, auch in
      einer verbesserten langfristigen Entwicklung der
      Pflanzenpopulationen münden, bleibt offen. Entsprechend
      unserer Ergebnisse hängt die Entwicklung von Populationen und
      Arten von einer Bandbreite vieler verschiedener Faktoren
      deren Interaktion ab. Diese müssen berücksichtigt werden,
      wenn es darum geht den momentanen Zustand und auch mögliche
      Zukunftsperspektiven von Pflanzenpopulationen zu
      beschreiben.