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Effects of frequency-dependence in maintaining diversity in coexisting ecologically similar species

Nilén, Sofie (2018) BIOK01 20181
Degree Projects in Biology
Abstract
Niche theory predicts that cooccurring species must differ in their use of environments in order to coexist, thereby diversity can be maintained in a community. However, ecologically similar species do frequently occur in nature, hence species inhabit similar physical environs and share single underling resources. In coexisting species with a similar niche, ecological drift is thought to eventually cause all but one species to go extinct, assuming drift acts alone. As drift is likely to be present in a community, contracting forces are expected to be found. One of those forces could be selection where frequency-dependence that can maintain diversity through e.g. rare species advantages and is thus capable of maintaining stable coexistence.... (More)
Niche theory predicts that cooccurring species must differ in their use of environments in order to coexist, thereby diversity can be maintained in a community. However, ecologically similar species do frequently occur in nature, hence species inhabit similar physical environs and share single underling resources. In coexisting species with a similar niche, ecological drift is thought to eventually cause all but one species to go extinct, assuming drift acts alone. As drift is likely to be present in a community, contracting forces are expected to be found. One of those forces could be selection where frequency-dependence that can maintain diversity through e.g. rare species advantages and is thus capable of maintaining stable coexistence. Here we investigate mechanisms that can maintain diversity in ecologically similar but evolutionary separated species of damselflies (I. elegans and E. cyathigerum). We regulated frequencies of both species in mesocosm experiments and mating trials and were able to experimentally demonstrate the importance of negative frequency-dependence (rare-species advantages) in maintaining diversity in ecologically similar species. (Less)
Popular Abstract
Rare species advantages solving the problems of coexistence

The maintenance of diversity in a community have long been explained by how species differ in their use of their environment. However, there are many examples in nature where similar species do cooccur in nature. For example, in Barro Colorado Island approximately 300 tree species were found in only 50 ha. This inevitably raises the question: How can so many closely related species coexist? Interestingly, closely related species of damselflies inhabit similar physical environments and often share single underlying resources. The minor differences of damselflies challenge traditional models of species coexistence.

Methods
We wanted to know how closely related species can... (More)
Rare species advantages solving the problems of coexistence

The maintenance of diversity in a community have long been explained by how species differ in their use of their environment. However, there are many examples in nature where similar species do cooccur in nature. For example, in Barro Colorado Island approximately 300 tree species were found in only 50 ha. This inevitably raises the question: How can so many closely related species coexist? Interestingly, closely related species of damselflies inhabit similar physical environments and often share single underlying resources. The minor differences of damselflies challenge traditional models of species coexistence.

Methods
We wanted to know how closely related species can be maintained in a community without outcompeting each other. As study organisms we used the two, co-occurring species of damselflies: The Blue-tailed damselfly (Ischnura elegans) and the common blue damselfly (Enallagma cyathigerum). The two species were kept in big outdoor cages simulating natural conditions where we wanted to understand how survival were affected by interference competition within and between species. We also used smaller cages where we looked at how mating effected both species. In both experiments we manipulated the frequencies of both species in experiments in three frequencies, (Rare: 25 %, Common: 75 % and Allopatric: 100 %) for the Blue-tailed damselfly and the common blue damselfly.

Results
We found that the Blue-tailed damselfly survived longer in all treatments compared to the common blue damselfly. As this species does better in all the treatments one would expect that this species will outcompete the common blue damselfly in their natural community. However, we also found that the Blue-tailed damselfly regulates its own abundance. When common the Blue- tailed damselfly will interact with itself more through interference competition which decreases its survival. When rare this species both survives longer and have a higher proportion of matings, which can affect population growth. I suggest that the combination of interference competition that can regulate the species abundance and through rare-specie advantages, diversity can be maintained, even if differences between species are small.


Supervisor: Miguel A. Gomez-Llano and Erik I. Svensson
Bachelor thesis 15 Credits BIOK01 2018
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Nilén, Sofie
supervisor
organization
course
BIOK01 20181
year
type
M2 - Bachelor Degree
subject
language
English
id
8962381
date added to LUP
2018-10-25 15:53:54
date last changed
2018-10-25 15:53:54
@misc{8962381,
  abstract     = {{Niche theory predicts that cooccurring species must differ in their use of environments in order to coexist, thereby diversity can be maintained in a community. However, ecologically similar species do frequently occur in nature, hence species inhabit similar physical environs and share single underling resources. In coexisting species with a similar niche, ecological drift is thought to eventually cause all but one species to go extinct, assuming drift acts alone. As drift is likely to be present in a community, contracting forces are expected to be found. One of those forces could be selection where frequency-dependence that can maintain diversity through e.g. rare species advantages and is thus capable of maintaining stable coexistence. Here we investigate mechanisms that can maintain diversity in ecologically similar but evolutionary separated species of damselflies (I. elegans and E. cyathigerum). We regulated frequencies of both species in mesocosm experiments and mating trials and were able to experimentally demonstrate the importance of negative frequency-dependence (rare-species advantages) in maintaining diversity in ecologically similar species.}},
  author       = {{Nilén, Sofie}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Effects of frequency-dependence in maintaining diversity in coexisting ecologically similar species}},
  year         = {{2018}},
}