To grow and survive or reproduce and die?: life-history strategies and ecological interactions between the mussels Mytilus edulis (Linnaeus, 1758) and Mytilus trossulus (Gould, 1850) in the Northwest Atlantic

• Main Author: Lowen, John Benjamin
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2008
• Subjects: Newfoundland; Northwest Atlantic
• Online Access: https://research.library.mun.ca/9402/; https://research.library.mun.ca/9402/1/Lowen_JohnBenjamin.pdf

The spatial and temporal distributions of two closely related blue mussel species (Mytilus edulis and M. trossulus) which co-exist within a mosaic hybrid zone in Newfoundland are not well understood. Where closely related species do not clearly differentiate along resource or physiological gradients, resource allocation to traits that enhance their ecological differentiation in fluctuating environments could stabilize their co-existence. Accordingly, a key objective of this study was to relate the plasticity of growth (which influences future survival), reproductive effort (which influences dispersal and colonization), and survival (linked to maintenance), among M. edulis, M. trossulus and their reciprocal F1 hybrids to variation in site productivity. The findings determined the design of a subsequent series of experiments, which focussed on predator inducible defenses and density dependent intra-specific and inter-specific interactions between M. edulis and M. trossulus. Reproductive cycles were generally similar among the parental species and F1 hybrids. Gamete output was significantly higher in M. trossulus than in M. edulis and the F1 hybrids. M. edulis prioritized allocation of resources to somatic traits (growth, shell thickness and adductor mass) to a greater extent than M trossulus, while M. trossulus prioritized allocation to reproduction (reproductive effort) to a greater degree than M. edulis. As in M. trossulus, but not in M. edulis, growth among sites in both hybrid groups did not change. Flexible allocation to reproduction among sites was evident in the F1 hybrids, but relative to M. trossulus overall reproductive effort was considerably lower. Hybrid edulis (M edulis female parent) survival was also lower than in both parental species, while hybrid trossulus (M. trossulus female parent) survival was not significantly different, although variation was greater in hybrid trossulus. These attributes likely reduce the establishment success of the F1 hybrid groups. In an experiment on predator induced ...