EEOB publications :: July 1 - July 31
Life in the fast lane: Revisiting the fast growth—High survival paradigm during the early life stages of fishes
Dominique Robert, Ignacio A. Catalán, Su Sponaugle, Evan K. D'Alessandro, John F. Dower, Louis Fortier, Alberto G. García, Klaus B. Huebert, Marc Hufnagl, Shin-ichi Ito, Mikimasa Joh, Jun Shoji, Pascal Sirois, Akinori Takasuka, Arild Folkvord, Patricia M. Ayón, Stuart A. Ludsin, Myron A. Peck, Richard D. Brodeur, Emily Y. Campbell, Francis Juanes, Mitsuo Nyuji, Yoshioki Oozeki, Motomitsu Takahashi, Yosuke Tanaka, Naoki Tojo, Naotaka Yasue, Pierre Pepin. 2023. Wiley Online. DOI: 10.1111/faf.12774
Early life survival is critical to successful replenishment of fish populations, and hy- potheses developed under the Growth-Survival Paradigm (GSP) have guided investiga- tions of controlling processes. The GSP postulates that recruitment depends on growth and mortality rates during early life stages, as well as their duration, after which the mortality declines substantially. The GSP predicts a shift in the frequency distribution of growth histories with age towards faster growth rates relative to the initial popula- tion because slow-growing individuals are subject to high mortality (via starvation and predation). However, mortality data compiled from 387 cases published in 153 stud- ies (1971–2022) showed that the GSP was only supported in 56% of cases. Selection against slow growth occurred in two-thirds of field studies, leaving a non-negligible fraction of cases showing either an absence of or inverse growth-selective survival, suggesting the growth-survival relationship is more complex than currently considered within the GSP framework. Stochastic simulations allowed us to assess the influence of key intrinsic and extrinsic factors on the characteristics of surviving larvae and identify knowledge gaps on the drivers of variability in growth-selective survival. We suggest caution when interpreting patterns of growth selection because changes in variance and autocorrelation of individual growth rates among cohorts can invalidate fundamen- tal GSP assumptions. We argue that breakthroughs in recruitment research require a comprehensive, population-specific characterization of the role of predation and intrin- sic factors in driving variability in the distribution and autocorrelation of larval growth rates, and of the life stage corresponding to the endpoint of pre-recruited life.
Comparative Phylogeography of Microsnails from the Pacific Northwest
Megan L. Smith, Connor Lang, David Sneddon, Jessica Wallace, Anahí Espíndola, Jack Sullivan, Bryan C. Carstens. Northwest Science, 96(1-2):117-132 (2023). doi.org/10.3955/046.096.0108
Leaf-litter-dwelling invertebrates serve an important role in ecosystem function by breaking down nutrients and potentially acting as indicators of habitat quality. However, this community is understudied due to difficulties related to sampling and taxonomic identification. To explore this community, we sampled leaf litter from the coastal and Cascade ranges of the Pacific Northwest of North America and searched > 200 samples for micro-invertebrates. We removed and photographed more than 400 invertebrate specimens, sequenced a portion of the mitochondrial gene cytochrome oxidase I (COI) for 60 samples, and used COI and the BLASTn database to identify invertebrates. Using these sequences and environmental data from the collection localities, we investigated the phylogeographic history of the two best-sampled species of microsnails, the toothless column snail (Columella edentula) and the conical spot snail (Punctum randolphii). Results suggest that populations of these species from the coastal and Cascade ranges may have survived in a single refugium during the Pleistocene glacial cycles and recolonized the coastal and Cascade ranges during the Holocene. Our results add to the knowledge of species responses to the Pleistocene glacial cycles in the Pacific Northwest and suggest that future studies should aim to increase representation of micro-invertebrates, perhaps using metabarcoding techniques.
Pleistocene glaciations caused the latitudinal gradient of within-species genetic diversity
Emanuel M Fonseca, Tara A Pelletier, Sydney K Decker, Danielle J Parsons, Bryan C Carstens. 2023. Evolution Letters, qrad030, doi.org/10.1093/evlett/qrad030
Intraspecific genetic diversity is a key aspect of biodiversity. Quaternary climatic change and glaciation influenced intraspecific genetic diversity by promoting range shifts and population size change. However, the extent to which glaciation affected genetic diversity on a global scale is not well established. Here we quantify nucleotide diversity, a common metric of intraspecific genetic diversity, in more than 38,000 plant and animal species using georeferenced DNA sequences from millions of samples. Results demonstrate that tropical species contain significantly more intraspecific genetic diversity than nontropical species. To explore potential evolutionary processes that may have contributed to this pattern, we calculated summary statistics that measure population demographic change and detected significant correlations between these statistics and latitude. We find that nontropical species are more likely to deviate from neutral expectations, indicating that they have historically experienced dramatic fluctuations in population size likely associated with Pleistocene glacial cycles. By analyzing the most comprehensive data set to date, our results imply that Quaternary climate perturbations may be more important as a process driving the latitudinal gradient in species richness than previously appreciated.
Genus-level revision of the Heterozerconoidea (Parasitiformes: Mesostigmata)
HANS KLOMPEN & BEVERLY S. GERDEMAN. 2023. Zootaxa 5322 (1): 001–066. doi.org/10.11646/zootaxa.5322.1.1
The genera of Heterozerconoidea are revised based on a species-level analysis of relationships in the group. The family Discozerconidae in its current state may be paraphyletic. Diagnoses for the genera are updated, and a catalog of all described species is provided. As part of this re-analysis two new genera, Amyzozercon and Ecuazercon, and four new species are described, and a key to the genera is provided. Possible evolutionary implications of the proposed set of relationships in terms of biogeography and the evolution of podospermy are discussed.