Bentzen, Paul
http://hdl.handle.net/10222/22289
2024-03-28T10:46:02ZBoth Geography and Ecology Contribute to Mating Isolation in Guppies
http://hdl.handle.net/10222/28715
Both Geography and Ecology Contribute to Mating Isolation in Guppies
Schwartz, Amy K.; Weese, Dylan J.; Bentzen, Paul; Kinnison, Michael T.; Hendry, Andrew P.
Local adaptation to different environments can promote mating isolation - either as an
incidental by-product of trait divergence, or as a result of selection to avoid maladaptive mating.
Numerous recent empirical examples point to the common influence of divergent natural selection on
speciation based largely on evidence of strong pre-mating isolation between populations from
different habitat types. Accumulating evidence for natural selection's influence on
speciation is therefore no longer a challenge. The difficulty, rather, is in determining the
mechanisms involved in the progress of adaptive divergence to speciation once barriers to gene flow
are already present. Here, we present results of both laboratory and field experiments with
Trinidadian guppies (Poecilia reticulata) from different environments, who do not show complete
reproductive isolation despite adaptive divergence. We investigate patterns of mating isolation
between populations that do and do not exchange migrants and show evidence for both by-product and
reinforcement mechanisms depending on female ecology. Specifically, low-predation females
discriminate against all high-predation males thus implying a by-product mechanism, whereas
high-predation females only discriminate against low-predation males from further upstream in the
same river, implying selection to avoid maladaptive mating. Our study thus confirms that mechanisms
of adaptive speciation are not necessarily mutually exclusive and uncovers the complex
ecology-geography interactions that underlie the evolution of mating isolation in nature.
2010-12-01T00:00:00ZIdentifying Canadian Freshwater Fishes through DNA Barcodes
http://hdl.handle.net/10222/28676
Identifying Canadian Freshwater Fishes through DNA Barcodes
Hubert, Nicolas; Hanner, Robert; Holm, Erling; Mandrak, Nicholas E.; Taylor, Eric; Burridge, Mary; Watkinson, Douglas; Dumont, Pierre; Curry, Allen; Bentzen, Paul; Zhang, Junbin; April, Julien; Bernatchez, Louis
Background: DNA barcoding aims to provide an efficient method for species-level identifications
using an array of species specific molecular tags derived from the 59 region of the mitochondrial
cytochrome c oxidase I (COI) gene. The efficiency of the method hinges on the degree of sequence
divergence among species and species-level identifications are relatively straightforward when the
average genetic distance among individuals within a species does not exceed the average genetic
distance between sister species. Fishes constitute a highly diverse group of vertebrates that
exhibit deep phenotypic changes during development. In this context, the identification of fish
species is challenging and DNA barcoding provide new perspectives in ecology and systematics of
fishes. Here we examined the degree to which DNA barcoding discriminate freshwater fish species from
the well-known Canadian fauna, which currently encompasses nearly 200 species, some which are of
high economic value like salmons and sturgeons. Methodology/Principal Findings: We bi-directionally
sequenced the standard 652 bp "barcode'' region of COI for 1360 individuals
belonging to 190 of the 203 Canadian freshwater fish species (95%). Most species were represented by
multiple individuals (7.6 on average), the majority of which were retained as voucher specimens. The
average genetic distance was 27 fold higher between species than within species, as K2P distance
estimates averaged 8.3% among congeners and only 0.3% among concpecifics. However, shared
polymorphism between sister-species was detected in 15 species (8% of the cases). The distribution
of K2P distance between individuals and species overlapped and identifications were only possible to
species group using DNA barcodes in these cases. Conversely, deep hidden genetic divergence was
revealed within two species, suggesting the presence of cryptic species. Conclusions/Significance:
The present study evidenced that freshwater fish species can be efficiently identified through the
use of DNA barcoding, especially the species complex of small-sized species, and that the present
COI library can be used for subsequent applications in ecology and systematics.
2008-06-01T00:00:00ZMixed evidence for reduced local adaptation in wild salmon resulting from interbreeding with
escaped farmed salmon: complexities in hybrid fitness
http://hdl.handle.net/10222/28669
Mixed evidence for reduced local adaptation in wild salmon resulting from interbreeding with
escaped farmed salmon: complexities in hybrid fitness
Fraser, Dylan J.; Cook, Adam M.; Eddington, James D.; Bentzen, Paul; Hutchings, Jeffrey A.
Interbreeding between artificially-selected and wild organisms can have negative fitness
consequences for the latter. In the Northwest Atlantic, farmed Atlantic salmon recurrently escape
into the wild and enter rivers where small, declining populations of wild salmon breed. Most farmed
salmon in the region derive from an ancestral source population that occupies a nonacidified river
(pH 6.0-6.5). Yet many wild populations with which escaped farmed salmon might interbreed inhabit
acidified rivers (pH 4.6-5.2). Using common garden experimentation, and examining two early-life
history stages across two generations of interbreeding, we showed that wild salmon populations
inhabiting acidified rivers had higher survival at acidified pH than farmed salmon or F(1)
farmed-wild hybrids. In contrast, however, there was limited evidence for reduced performance in
backcrosses, and F(2) farmed-wild hybrids performed better or equally well to wild salmon. Wild
salmon also survived or grew better at nonacidified than acidified pH, and wild and farmed salmon
survived equally well at nonacidified pH. Thus, for acid tolerance and the stages examined, we found
some evidence both for and against the theory that repeated farmed-wild interbreeding may reduce
adaptive genetic variation in the wild and thereby negatively affect the persistence of depleted
wild populations.
2008-08-01T00:00:00ZPopulation Structure as Revealed by mtDNA and Microsatellites in Northern Fur Seals, Callorhinus
ursinus, throughout Their Range
http://hdl.handle.net/10222/28660
Population Structure as Revealed by mtDNA and Microsatellites in Northern Fur Seals, Callorhinus
ursinus, throughout Their Range
Dickerson, Bobette R.; Ream, Rolf R.; Vignieri, Sacha N.; Bentzen, Paul
Background: The northern fur seal (Callorhinus ursinus; NFS) is a widely distributed pinniped
that has been shown to exhibit a high degree of philopatry to islands, breeding areas on an island,
and even to specific segments of breeding areas. This level of philopatry could conceivably lead to
highly genetically divergent populations. However, northern fur seals have the potential for
dispersal across large distances and have experienced repeated rapid population expansions following
glacial retreat and the more recent cessation of intensive harvest pressure. Methodology/Principal
Findings: Using microsatellite and mitochondrial loci, we examined population structure in NFS
throughout their range. We found only weak population genetic structure among breeding islands
including significant F(ST) and Phi(ST) values between eastern and western Pacific islands.
Conclusions: We conclude that insufficient time since rapid population expansion events (both post
glacial and following the cessation of intense harvest pressure) mixed with low levels of
contemporary migration have resulted in an absence of genetic structure across the entire northern
fur seal range.
2010-05-01T00:00:00Z