東華大學圖書館 |

Plastic Morphology and Trophic Flexibility: Understanding Environmental Drivers and Evolutionary Implications of Intraspecific Variation in Gorgonian Octocorals /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Plastic Morphology and Trophic Flexibility: Understanding Environmental Drivers and Evolutionary Implications of Intraspecific Variation in Gorgonian Octocorals // Rachael M Best.
作者:	Best, Rachael M.,
面頁冊數:	1 electronic resource (102 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-03, Section: B.
Contained By:	Dissertations Abstracts International86-03B.
標題:	Biology. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31237406
ISBN:	9798384046332

Plastic Morphology and Trophic Flexibility: Understanding Environmental Drivers and Evolutionary Implications of Intraspecific Variation in Gorgonian Octocorals /
Best, Rachael M.,

Plastic Morphology and Trophic Flexibility: Understanding Environmental Drivers and Evolutionary Implications of Intraspecific Variation in Gorgonian Octocorals /Rachael M Best. - 1 electronic resource (102 pages)

Source: Dissertations Abstracts International, Volume: 86-03, Section: B.

Sessile marine organisms often exhibit intraspecific variation in response to their environment as a result of genetic differences or phenotypic plasticity. Common visible intraspecific variation includes color, morphology, and trophic ecology. Some of the most colorful marine organisms are sessile, with bright coloration and an abundance of color polymorphisms. The asymbiotic octocoral Leptogorgia virgulata is one species with strong color polymorphisms, existing predominantly in yellow, orange, and magenta morphs. Coloration in L. virgulata is genetically determined and is hypothesized to be controlled by one gene with at least four alleles. We documented the distribution of color morphs at inshore and offshore sites in the northeastern Gulf of Mexico and found differential color distribution. All three color morphs inhabit inshore sites, although colonies in these populations are predominately magenta and yellow, while offshore populations consist nearly entirely magenta morphs. We documented differences in micromorphological traits between yellow and magenta color morphs, including an increase in polyp density and a decrease in sclerite width in yellow morphs. However, through a laboratory spawning experiment and genetic analyses, we verified that the color morphs at inshore and offshore sites show genetic similarity with no observed barriers to cross-fertilization. Using a transplant experiment, we determined that both magenta and yellow colonies respond plastically in relative growth rate when transplanted between inshore and offshore sites. Within each location, magenta and yellow morphs did not differ from one another in relative growth. However, there was a significant interaction between color morph and location, as magenta morphs decreased their relative growth significantly more than yellow morphs, regressing on average, when transplanted offshore. We hypothesize that the differential distribution in color morphs between environments may be due to fitness tradeoffs between morphology and compound composition linked with color morphs. We suspect that the nearly 20% increase in polyp density associated with the yellow morph requires increased energy demands, which may be costly under lower nutrient levels at offshore sites. Because inshore and offshore sites show considerable differences in environmental variation, we investigated whether populations of L. virgulata exhibit phenotypic plasticity genotype-by-environment interactions. Phenotypic plasticity is one mechanism by which organisms can quickly respond within a generation to changing or variable environmental conditions, which can especially be beneficial for sessile organisms. Most studies examining phenotypic plasticity in sessile cnidarians have focused on species that host obligate, photosynthetic algal symbionts, such as hard corals, octocorals, and anemones. Symbiotic octocoral species have been shown to vary across depth, where nearshore individuals often have higher branch and polyp densities. These plastic traits are often attributed to variation in light availability and hydrodynamics across depth. However, to understand the evolutionary drivers of plasticity in symbiotic organisms, it is important to consider the influences of both host and endosymbiont. Previous studies on phenotypic plasticity in octocorals have uncovered some general trends in morphological responses to changes in depth that are often attributed to changes in light availability. However, these studies examined plasticity in octocoral species that host endosymbiotic algae, yet many species of octocorals are asymbiotic. Asymbiotic species, therefore, may not respond in similar ways due to the lack of reliance on endosymbiont photosynthesis. We documented intraspecific variation in L. virgulata in response to inshore and offshore sites to investigate changes displayed by a cnidarian outside of the demands of photosynthetic symbionts. Because of the difference in color distribution and the associated morphological differences between magenta and yellow morphs, we investigated intraspecific variation between inshore and offshore sites using magenta morphs only. We found that L. virgulata, similar to symbiotic octocoral species, exhibits increased branching at inshore sites, indicating that variation in branching can occur in the absence of reliance on light availability for photosynthesis. In contrast, we did not find variation in polyp density. Using a reciprocal transplant of magenta morphs across three sites varying in their distance from shore, we uncovered phenotypic plasticity for both relative growth rate and branching. Additionally, we found significant genotype-by-environment interactions that varied based on both the origin and transplant destination of the L. virgulata genotypes. Our findings highlight the ways in which octocorals can respond plastically to the environment and the potential of drivers that influence the evolution of plasticity.Morphological variation in response to the environment can result in shifts in trophic ecology. Trophic strategy can vary both inter- and intraspecifically in response to changes in the morphology, behavior, or the environment. In several endosymbiotic scleractinians and octocorals, having larger polyps is often correlated with increased reliance on heterotrophic feeding across species; species with smaller polyps are more reliant on their autotrophic endosymbionts. However, little is known about whether this relationship between polyp morphology and trophic strategy exists intraspecifically in octocorals. We quantified variation in polyp tentacle length within the endosymbiotic octocoral genus Pseudoplexaura across depth on reefs in the U.S. Virgin Islands and found a significant positive relationship between depth and tentacle length. Using tissue samples from P. porosa and P. wagenaari, we compared trophic ecology in relation to variation in polyp size using a Bayesian analysis of stable carbon and nitrogen isotopes. We found that across tentacle lengths, P. wagenaari is principally heterotrophic. However, P. porosa exhibits trophic strategy variation associated with tentacle length, shifting from mainly autotrophy to mixotrophy with increased tentacle length. Our study documents species-specific trophic strategies linked with variation in morphology and trophic flexibility within the same environmental conditions, uncovering potential niche differentiation both within and between species in tropical octocorals.

English

ISBN: 9798384046332Subjects--Topical Terms:

522710
Biology.
Subjects--Index Terms:

Genotype-by-environment Interaction

Plastic Morphology and Trophic Flexibility: Understanding Environmental Drivers and Evolutionary Implications of Intraspecific Variation in Gorgonian Octocorals /
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520 $a Sessile marine organisms often exhibit intraspecific variation in response to their environment as a result of genetic differences or phenotypic plasticity. Common visible intraspecific variation includes color, morphology, and trophic ecology. Some of the most colorful marine organisms are sessile, with bright coloration and an abundance of color polymorphisms. The asymbiotic octocoral Leptogorgia virgulata is one species with strong color polymorphisms, existing predominantly in yellow, orange, and magenta morphs. Coloration in L. virgulata is genetically determined and is hypothesized to be controlled by one gene with at least four alleles. We documented the distribution of color morphs at inshore and offshore sites in the northeastern Gulf of Mexico and found differential color distribution. All three color morphs inhabit inshore sites, although colonies in these populations are predominately magenta and yellow, while offshore populations consist nearly entirely magenta morphs. We documented differences in micromorphological traits between yellow and magenta color morphs, including an increase in polyp density and a decrease in sclerite width in yellow morphs. However, through a laboratory spawning experiment and genetic analyses, we verified that the color morphs at inshore and offshore sites show genetic similarity with no observed barriers to cross-fertilization. Using a transplant experiment, we determined that both magenta and yellow colonies respond plastically in relative growth rate when transplanted between inshore and offshore sites. Within each location, magenta and yellow morphs did not differ from one another in relative growth. However, there was a significant interaction between color morph and location, as magenta morphs decreased their relative growth significantly more than yellow morphs, regressing on average, when transplanted offshore. We hypothesize that the differential distribution in color morphs between environments may be due to fitness tradeoffs between morphology and compound composition linked with color morphs. We suspect that the nearly 20% increase in polyp density associated with the yellow morph requires increased energy demands, which may be costly under lower nutrient levels at offshore sites. Because inshore and offshore sites show considerable differences in environmental variation, we investigated whether populations of L. virgulata exhibit phenotypic plasticity genotype-by-environment interactions. Phenotypic plasticity is one mechanism by which organisms can quickly respond within a generation to changing or variable environmental conditions, which can especially be beneficial for sessile organisms. Most studies examining phenotypic plasticity in sessile cnidarians have focused on species that host obligate, photosynthetic algal symbionts, such as hard corals, octocorals, and anemones. Symbiotic octocoral species have been shown to vary across depth, where nearshore individuals often have higher branch and polyp densities. These plastic traits are often attributed to variation in light availability and hydrodynamics across depth. However, to understand the evolutionary drivers of plasticity in symbiotic organisms, it is important to consider the influences of both host and endosymbiont. Previous studies on phenotypic plasticity in octocorals have uncovered some general trends in morphological responses to changes in depth that are often attributed to changes in light availability. However, these studies examined plasticity in octocoral species that host endosymbiotic algae, yet many species of octocorals are asymbiotic. Asymbiotic species, therefore, may not respond in similar ways due to the lack of reliance on endosymbiont photosynthesis. We documented intraspecific variation in L. virgulata in response to inshore and offshore sites to investigate changes displayed by a cnidarian outside of the demands of photosynthetic symbionts. Because of the difference in color distribution and the associated morphological differences between magenta and yellow morphs, we investigated intraspecific variation between inshore and offshore sites using magenta morphs only. We found that L. virgulata, similar to symbiotic octocoral species, exhibits increased branching at inshore sites, indicating that variation in branching can occur in the absence of reliance on light availability for photosynthesis. In contrast, we did not find variation in polyp density. Using a reciprocal transplant of magenta morphs across three sites varying in their distance from shore, we uncovered phenotypic plasticity for both relative growth rate and branching. Additionally, we found significant genotype-by-environment interactions that varied based on both the origin and transplant destination of the L. virgulata genotypes. Our findings highlight the ways in which octocorals can respond plastically to the environment and the potential of drivers that influence the evolution of plasticity.Morphological variation in response to the environment can result in shifts in trophic ecology. Trophic strategy can vary both inter- and intraspecifically in response to changes in the morphology, behavior, or the environment. In several endosymbiotic scleractinians and octocorals, having larger polyps is often correlated with increased reliance on heterotrophic feeding across species; species with smaller polyps are more reliant on their autotrophic endosymbionts. However, little is known about whether this relationship between polyp morphology and trophic strategy exists intraspecifically in octocorals. We quantified variation in polyp tentacle length within the endosymbiotic octocoral genus Pseudoplexaura across depth on reefs in the U.S. Virgin Islands and found a significant positive relationship between depth and tentacle length. Using tissue samples from P. porosa and P. wagenaari, we compared trophic ecology in relation to variation in polyp size using a Bayesian analysis of stable carbon and nitrogen isotopes. We found that across tentacle lengths, P. wagenaari is principally heterotrophic. However, P. porosa exhibits trophic strategy variation associated with tentacle length, shifting from mainly autotrophy to mixotrophy with increased tentacle length. Our study documents species-specific trophic strategies linked with variation in morphology and trophic flexibility within the same environmental conditions, uncovering potential niche differentiation both within and between species in tropical octocorals.
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