Evaluating a pattern of ecological character displacement: charr jaw morphology and diet diverge in sympatry versus allopatry across catchments in Hokkaido, Japan

2019 ◽  
Vol 129 (2) ◽  
pp. 356-378 ◽  
Author(s):  
Shigeru Nakano ◽  
Kurt D Fausch ◽  
Itsuro Koizumi ◽  
Yoichiro Kanno ◽  
Yoshinori Taniguchi ◽  
...  
Keyword(s):  
Phenotypic Plasticity ◽  
Character Displacement ◽  
Invertebrate Drift ◽  
Similar Species ◽  
Dolly Varden ◽  
Terrestrial Invertebrates ◽  
Rapid Responses ◽  
Close Proximity ◽  
Foraging Modes ◽  
Significant Divergence

Abstract Similar species that overlap in sympatry may diverge in characters related to resource use as a result of evolution or phenotypic plasticity. Dolly Varden charr (Salvelinus malma) and whitespotted charr (S. leucomaenis) overlap along streams in Hokkaido, Japan, and compete by interference for invertebrate drift-foraging positions. Previous research has shown that as drift declines during summer, Dolly Varden shift foraging modes to capture benthic prey, a behaviour facilitated by their subterminal jaw morphology. We compare body and jaw morphology of Dolly Varden in sympatry vs. allopatry in two locations to test for character displacement. Statistical analysis showed significant divergence in characters related to foraging, which was correlated with variation in individual charr diets. Dolly Varden in sympatry had shorter heads and lower jaws than in allopatry, and even within sites charr with these characteristics fed less on drifting terrestrial invertebrates but more on benthic aquatic invertebrates. Those in allopatry had longer heads and lower jaws, and fed more on terrestrial invertebrates. The close proximity of sites in one stream suggests that Dolly Varden may display phenotypic plasticity similar to other charr, allowing rapid responses in morphology to the presence of competitors. These morphological shifts probably help them maintain positive fitness when competing with whitespotted charr in Hokkaido streams.

scholarly journals The effects of riparian forestry on invertebrate drift and brown trout in upland streams of contrasting acidity

2004 ◽  
Vol 8 (3) ◽  
pp. 578-588 ◽  
Author(s):  
S. J. Ormerod ◽  
M. E. Jones ◽  
M. C. Jones ◽  
D. R. Phillips
Keyword(s):  
Land Use ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Benthic Invertebrate ◽  
Acid Sites ◽  
Invertebrate Drift ◽  
Conifer Forest ◽  
Terrestrial Invertebrates ◽  
Invertebrate Abundance ◽  
Drift Density

Abstract. Variations in macroinvertebrate drift and benthic invertebrate abundance were assessed in 30 upland Welsh streams of varying acidity (pH < 5.7 or pH.> 6.0) and riparian land-use (conifer, moorland or native broadleaf). The consequences for the diet and condition of wild brown trout Salmo trutta were also assessed. As expected from previous studies, there were significant reductions in benthic invertebrate abundance, aquatic drift density (by >60%), aquatic drift biomass (by >35%), total drift density (by >35%) and total drift biomass (by >20%) at acid sites by comparison with circumneutral sites due largely to the scarcity of mayflies. Absolute drift from terrestrial sources was unrelated to stream pH but formed a significantly greater proportion of total drift at acid sites (30-65% of density) than at circumneutral sites (20-40%) as aquatic contributions declined. Most of this apparent land use effect reflected significantly increased terrestrial drift under broadleaves. There was no significant reduction in terrestrial or aquatic drift at conifer forest sites per se after accounting for low pH. Trout diet varied substantially between locations partly reflecting variations in drift: significantly fewer mayflies and stoneflies were eaten at acid sites, and significantly more terrestrial prey were eaten under broadleaves. However, acidity did not reduce trout condition or gut-fullness. Unexpectedly, trout condition was significantly enhanced at conifer sites, irrespective of their pH. Hence, acidity has greater effects on the benthic abundance and drift density of invertebrates in upland streams than does riparian land use. However, trout forage flexibly enough to offset any possible food deficit, for example by switching to chironomids and terrestrial invertebrates. Enhanced terrestrial contributions to invertebrate drift from riparian broadleaf trees may be important in supplementing foraging opportunities for trout where aquatic prey are scarce. These data illustrate the value of native tree species in riparian locations in upland Britain and the energy subsidy they provide might well be disproportionately important for otherwise impoverished acid streams Keywords: brown trout, land-use, acidification, drift, forestry, streams

scholarly journals Range-wide spatial mapping reveals convergent character displacement of bird song

2019 ◽  
Vol 286 (1902) ◽  
pp. 20190443 ◽  
Author(s):  
Alexander N. G. Kirschel ◽  
Nathalie Seddon ◽  
Joseph A. Tobias
Keyword(s):  
Spatial Patterns ◽  
Evolutionary Biology ◽  
Environmental Gradients ◽  
Empirical Studies ◽  
Remote Sensing Data ◽  
Character Displacement ◽  
Similar Species ◽  
Interspecific Territoriality ◽  
Coexisting Species

A long-held view in evolutionary biology is that character displacement generates divergent phenotypes in closely related coexisting species to avoid the costs of hybridization or ecological competition, whereas an alternative possibility is that signals of dominance or aggression may instead converge to facilitate coexistence among ecological competitors. Although this counterintuitive process—termed convergent agonistic character displacement—is supported by recent theoretical and empirical studies, the extent to which it drives spatial patterns of trait evolution at continental scales remains unclear. By modelling the variation in song structure of two ecologically similar species of Hypocnemis antbird across western Amazonia, we show that their territorial signals converge such that trait similarity peaks in the sympatric zone, where intense interspecific territoriality between these taxa has previously been demonstrated. We also use remote sensing data to show that signal convergence is not explained by environmental gradients and is thus unlikely to evolve by sensory drive (i.e. acoustic adaptation to the sound transmission properties of habitats). Our results suggest that agonistic character displacement driven by interspecific competition can generate spatial patterns opposite to those predicted by classic character displacement theory, and highlight the potential role of social selection in shaping geographical variation in signal phenotypes of ecological competitors.

scholarly journals Nests in the cities: adaptive and non-adaptive phenotypic plasticity and convergence in an urban bird

2020 ◽  
Vol 287 (1941) ◽  
pp. 20202122
Author(s):  
Samuel A. Bressler ◽  
Eleanor S. Diamant ◽  
Morgan W. Tingley ◽  
Pamela J. Yeh
Keyword(s):  
Phenotypic Plasticity ◽  
Los Angeles ◽  
San Diego ◽  
Critical Role ◽  
Urban Ecosystems ◽  
Urban Environments ◽  
Behavioural Plasticity ◽  
Nesting Biology ◽  
Urban Populations ◽  
Rapid Responses

Phenotypic plasticity plays a critical role in adaptation to novel environments. Behavioural plasticity enables more rapid responses to unfamiliar conditions than evolution by natural selection. Urban ecosystems are one such novel environment in which behavioural plasticity has been documented. However, whether such plasticity is adaptive, and if plasticity is convergent among urban populations, is poorly understood. We studied the nesting biology of an ‘urban-adapter’ species, the dark-eyed junco ( Junco hyemalis ), to understand the role of plasticity in adapting to city life. We examined (i) whether novel nesting behaviours are adaptive, (ii) whether pairs modify nest characteristics in response to prior outcomes, and (iii) whether two urban populations exhibit similar nesting behaviour. We monitored 170 junco nests in urban Los Angeles and compared our results with prior research on 579 nests from urban San Diego. We found that nests placed in ecologically novel locations (off-ground and on artificial surfaces) increased fitness, and that pairs practiced informed re-nesting in site selection. The Los Angeles population more frequently nested off-ground than the San Diego population and exhibited a higher success rate. Our findings suggest that plasticity facilitates adaptation to urban environments, and that the drivers behind novel nesting behaviours are complex and multifaceted.

Foraging modes and movements of Oncorhynchus mykiss as flow and invertebrate drift recede in a California stream

2021 ◽  
Author(s):  
Gabriel J. Rossi ◽  
Mary E. Power ◽  
Shelley Pneh ◽  
Jason R Neuswanger ◽  
Timothy J. Caldwell
Keyword(s):  
Oncorhynchus Mykiss ◽  
Behavioral Flexibility ◽  
Late Summer ◽  
Additive Models ◽  
Invertebrate Drift ◽  
Low Velocity ◽  
Bioenergetic Model ◽  
Foraging Mode ◽  
Prey Concentration ◽  
Foraging Modes

Salmonids frequently adapt their feeding and movement strategies to cope with seasonally fluctuating stream environments. Oncorhynchus mykiss tend to drift-forage in higher velocity habitat than other salmonids, yet their presence in streams with seasonally low velocity and drift suggests behavioral flexibility. We combined 3-D videogrammetry with measurements of invertebrate drift and stream hydraulics to investigate the drivers of O. mykiss foraging mode and movement during the seasonal recession in a California stream. From May to July (2016), foraging movement rate increased as prey concentration and velocity declined; however, movement decreased in August as pools became low and still. In May, 80% of O. mykiss were drift-foraging, while by July, over 70% used search or benthic-foraging modes. Velocity and riffle crest depth were significant predictors of foraging mode, while drift concentration was a poor univariate predictor. However top ranked additive models included both hydraulic variables and drift concentration. A drift-foraging bioenergetic model was a poor predictor of foraging mode. We suggest that infall and benthic prey, as well as risk aversion, may influence late-summer foraging decisions.

scholarly journals Habitat-specific production of aquatic and terrestrial invertebrate drift in small forest streams: implications for drift-feeding fish

2017 ◽  
Vol 74 (8) ◽  
pp. 1208-1217 ◽  
Author(s):  
Sean M. Naman ◽  
Jordan S. Rosenfeld ◽  
Laura C. Third ◽  
John S. Richardson
Keyword(s):  
Prey Availability ◽  
Channel Structure ◽  
Invertebrate Drift ◽  
Entry Rate ◽  
Terrestrial Invertebrates ◽  
Drift Feeding ◽  
Drift Flux ◽  
Forest Streams ◽  
Channel Unit ◽  
Small Forest

The influence of stream channel structure on the production of prey for drift-feeding fish is not well understood. We quantified drift production, the entry rate per streambed area, and drift flux, the total export rate per channel unit, in three second-order, forested streams in southwest British Columbia, Canada. We tested whether (1) drift production was higher in riffles than in pools, (2) drift flux increased with riffle length, and (3) prey body size was larger from riffles relative to pools and from terrestrial drop relative to aquatic drift. Total and aquatic-derived drift production (mg·m−2·h−1) was ∼3.5 times higher in riffles relative to pools; however, terrestrial drift did not differ between channel types. Total drift flux (mg·h−1) was positively related to riffle length. Terrestrial invertebrates were approximately three times larger than aquatics, and invertebrates from riffles were approximately three times larger on average than those from pools. These results suggest that channel structure directly affects prey availability and prey quality for drift-feeding fish and that long riffles may be key areas of prey generation.

scholarly journals Range-wide spatial mapping reveals convergent character displacement of bird song

2019 ◽  
Author(s):  
Alexander N. G. Kirschel ◽  
Nathalie Seddon ◽  
Joseph A. Tobias
Keyword(s):  
Spatial Patterns ◽  
Evolutionary Biology ◽  
Environmental Gradients ◽  
Empirical Studies ◽  
Remote Sensing Data ◽  
Character Displacement ◽  
Similar Species ◽  
Interspecific Territoriality ◽  
Coexisting Species

AbstractA long-held view in evolutionary biology is that character displacement generates divergent phenotypes in closely related coexisting species to avoid the costs of hybridisation or ecological competition, whereas an alternative possibility is that signals of dominance or aggression may instead converge to facilitate coexistence among ecological competitors. Although this counter-intuitive process—termed convergent agonistic character displacement—is supported by recent theoretical and empirical studies, the extent to which it drives spatial patterns of trait evolution at continental scales remains unclear. By modeling variation in song structure of two ecologically similar species of Hypocnemis antbird across western Amazonia, we show that their territorial signals converge such that trait similarity peaks in the sympatric zone, where intense interspecific territoriality between these taxa has previously been demonstrated. We also use remote sensing data to show that signal convergence is not explained by environmental gradients and is thus unlikely to evolve by sensory drive (i.e. acoustic adaptation to the sound transmission properties of habitats). Our results suggest that agonistic character displacement driven by interspecific competition can generate spatial patterns opposite to those predicted by classic character displacement theory, and highlight the potential role of social selection in shaping geographical variation in signal phenotypes of ecological competitors.

scholarly journals Phenotypic plasticity revealed by molecular studies on reef corals of Fungia (Cycloseris) spp. (Scleractinia: Fungiidae) near river outlets

2006 ◽  
Vol 75 (03-04) ◽  
pp. 195-201 ◽  
Author(s):  
Adriaan Gittenberger ◽  
Bert W. Hoeksema
Keyword(s):  
Phenotypic Plasticity ◽  
Sea Water ◽  
Patch Reef ◽  
Mutual Distance ◽  
Allozyme Electrophoresis ◽  
Reef Corals ◽  
Close Proximity ◽  
Molecular Studies ◽  
Mushroom Coral ◽  
Field Area

On a patch reef off Makassar, Sulawesi, Indonesia, corals identified as Fungia (Cycloseris) costulata, Fungia (Cycloseris) tenuis and Fungia (Cycloseris) cf costulata were collected down to a maximum depth of 10 m. The corals lived sympatrically. Mushroom coral clones resulting from fragmentation can be recognized by their equal coloration and close proximity. Therefore, to ensure that no clones were collected, corals of dissimilar colors were selected at a mutual distance of 5 m. The corals were kept alive in two 30 liter sea-water aquariums with an air-pump. They were photographed in detail. Using allozyme electrophoresis in a laboratory close to the field area, it was tested whether the separate coral morphs should be considered three species. Eventually it was concluded that there are only two species, i.e. F. (C.) costulata and F. (C.) tenuis, of which F. (C.) costulata has two distinct morphs, one of which may be an eco-phenotype occurring on reefs off river outlets or inside estuaries.

Allozymic Variation and Species Diversity in North American Bosminidae

1994 ◽  
Vol 51 (4) ◽  
pp. 873-880 ◽  
Author(s):  
Rita De Melo ◽  
Paul D. N. Hebert
Keyword(s):  
Phenotypic Plasticity ◽  
Species Diversity ◽  
Genetic Variability ◽  
North American ◽  
Species Boundaries ◽  
Similar Species ◽  
Allozyme Analysis ◽  
Allozyme Data ◽  
Polymorphic Loci ◽  
Morphological Studies

North American members of the genus Bosmina show marked morphological variation and integradation, which have been attributed to the occurrence of both phenotypic plasticity and occasional hybridization between a small number of species. We employed allozyme analysis on 72 bosminid populations from 62 North American habitats to ascertain the validity of species boundaries and to verify the occurrence of hybridization. Results showed that levels of genetic variability (15.8% polymorphic loci, 10% individual heterozygosities) in bosminids were comparable with those reported in other zooplankton groups. Significant Hardy–Weinberg deviations were detected at 38% of polymorphic loci and were usually due to heterozygote deficiency. No clear evidence of interspecific hybridization was obtained, although some cases of heterozygote excess require further investigation. While prior morphological studies indicated the occurrence of only six species, the allozyme data revealed the presence of eight assemblages showing allelic substitutions at one or more loci. Each assemblage corresponded to a different species belonging to one of four subgenera (Bosmina, Eubosmina, Neobosmina, or Sinobosmina). Within two assemblages, individuals could be further partitioned into two morphologically distinct, but genetically similar species, leading to the recognition of 10 species in this study.

Taxonomic reassessment of Gracilaria cearensis (Rhodophyta, Gracilariales), a poorly defined yet common flattened species based on morphological and molecular analysis including topotype collections

Phytotaxa ◽  
2015 ◽  
Vol 201 (4) ◽  
pp. 241 ◽  
Author(s):  
Luanda Pereira Soares ◽  
Carlos Frederico Deluqui Gurgel ◽  
Mutue Toyota Fujii
Keyword(s):  
Phenotypic Plasticity ◽  
Genetic Divergence ◽  
Sequence Divergence ◽  
Taxonomic Status ◽  
Original Description ◽  
Distinct Species ◽  
Molecular Data ◽  
Rbcl Gene ◽  
Similar Species ◽  
The World

The genus Gracilaria is the major source of agarose in the world today and is one of the most species-rich genera in the Rhodophyta. Flat Gracilaria species are among the most taxonomically challenging taxa due to their widespread phenotypic plasticity among all species. Gracilaria cearensis is a flat species described in 1965 from Brazil. Its original description is not conducive to accurate taxonomic identifications and the delineation of this taxon remains elusive. New samples of G. cearensis were collected across a coastal length of 500 km including its type locality. Universal Plastid Amplicon (UPA) and the rbcL gene were used to confirm the phylogenetic and taxonomic status of this poorly known species. Results showed that this is a distinct species despite morphological similarities to G. hayi, G. cuneata, G. curtissiae, G. brasiliensis and G. galetensis. G. cearensis is sister to G. hayi yet the genetic divergence between these two species was 2% for rbcL and 1.08% for UPA, enough to consider them distinct taxa. However, newly generated molecular data placed G. smithsoniensis, another morphologically similar species, as conspecific with G. cearensis with only 0.07% rbcL sequence divergence between them.

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