Temporal scope influences ecosystem driver-response relationships: A case study of Lake Erie with implications for ecosystem-based management

Michael E. Fraker, James S. Sinclair, Kenneth T.Frank, James M. Hood, Stuart A. Ludsin. Science of The Total Environment, Volume 813, 2022, 152473, ISSN 0048-9697,

Abstract

Understanding environmental driver-response relationships is critical to the implementation of effective ecosystem-based management. Ecosystems are often influenced by multiple drivers that operate on different timescales and may be nonstationary. In turn, contrasting views of ecosystem state and structure could arise depending on the temporal perspective of analysis. Further, assessment of multiple ecosystem components (e.g., biological indicators) may serve to identify different key drivers and connections. To explore how the timescale of analysis and data richness can influence the identification of driver-response relationships within a large, dynamic ecosystem, this study analyzed long-term (1969–2018) data from Lake Erie (USA–Canada). Data were compiled on multiple biological, physical, chemical, and socioeconomic components of the ecosystem to quantify trends and identify potential key drivers during multiple time intervals (20 to 50 years duration), using zooplankton, bird, and fish community metrics as indicators of ecosystem change. Concurrent temporal shifts of many variables occurred during the 1980s, but asynchronous dynamics were evident among indicator taxa. The strengths and rank orders of predictive drivers shifted among intervals and were sometimes taxon-specific. Drivers related to nutrient loading and lake trophic status were consistently strong predictors of temporal patterns for all indicators; however, within the longer intervals, measures of agricultural land use were the strongest predictors, whereas within shorter intervals, the stronger predictors were measures of tributary or in-lake nutrient concentrations. Physical drivers also tended to increase in predictive ability within shorter intervals. The results highlight how the time interval examined can filter influences of lower-frequency, slower drivers and higher-frequency, faster drivers. Understanding ecosystem change in support of ecosystem-based management requires consideration of both the temporal perspective of analysis and the chosen indicators, as both can influence which drivers are identified as most predictive of ecosystem trends at that timescale.

Angler Choices That Help Catch Lots of Big Fish

Andrew P. Bade, David A. Dippold, Brian A. Schmidt, Mark R. DuFour, Travis J. Hartman, Stuart A. Ludsin. 2022. https://doi.org/10.1002/fsh.10722

Abstract

A primary goal of fisheries management is to maximize angler satisfaction (e.g., by catching more and bigger fish), while maintaining sustainable populations. In addition to environmental and ecological factors, angler choices may influence recreational catches. Using interviews (92,838) from Walleye (Sander vitreus) anglers in Lake Erie during 1989-2017, we identified how angler behavior influences catch outcomes. Angler behaviors were associated with changes in catch rate and the length of harvested fish. For example, trolling resulted in a 50% increase in median catch and 24 mm increase in length, relative to casting. Other behaviors led to tradeoffs between catch rate and size, such as the time of year anglers fished. We identified behaviors that maximize fishing success with respect to anglers’ desired catch outcomes. Our results can help increase angler satisfaction by providing realistic catch expectations given environmental and fishery conditions, while improving recreational catch outcomes through more informed angler-decision making.

Anchored hybrid enrichment resolves the phylogeny of Lacunicambarus Hobbs, 1969 (Decapoda: Astacidea: Cambaridae)

Mael G Glon, Michael B Broe, Keith A Crandall, Meg Daly, Sungsik Kong, Roger F Thoma, John V Freudenstein. Journal of Crustacean Biology, Volume 42, Issue 1, March 2022, ruab073,

Abstract

The taxonomy of North American crayfishes has recently experienced a boom in interest as these crustaceans have become increasingly imperiled. Improving taxonomic resolution can inform and facilitate conservation efforts but has proven challenging for crayfishes due to the limited number of molecular tools available to resolve species complexes and delimit species. The burrowing crayfish Lacunicambarus Hobbs, 1969 has a particularly convoluted taxonomic history that epitomizes many of the challenges of crayfish taxonomy. Recent studies using mitochondrial DNA (mtDNA) data to resolve this genus have had mixed results: mtDNA data have successfully resolved species-clades within Lacunicambarus but have failed to resolve interspecific relationships. This has precluded research on evolutionary history and biogeography. Our goal was to resolve the phylogeny of Lacunicambarus using anchored hybrid enrichment (AHE) data, a new source of additional molecular markers for estimating phylogenetic relationships. We present the best resolved phylogeny for Lacunicambarus to date and explore discrepancies between this phylogeny and past ones based on mtDNA data. We use this new phylogeny to explore interspecific relationships within Lacunicambarus and redescribe L. erythrodactylus (Simon & Morris, 2014) and L. nebrascensis (Girard, 1852) comb. nov. Our study demonstrates the tremendous contributions that next-generation sequencing methods like AHE can make to crayfish taxonomy and conservation.

Assessing model adequacy leads to more robust phylogeographic inference

Bryan C.Carstens, Megan L.Smith, Drew J.Duckett, Emanuel M.Fonseca, M. Tereza C.Thomé. Trends in Ecology & Evolution, 2022, ISSN 0169-5347.

Highlights

Phylogeography makes inferences about the evolutionary history of species by using statistical models of historical demography to analyze genetic data. These models are increasingly complex and sometimes applied in ways that can compromise the quality of phylogeographic inference.

Inferences are most often derived from estimates of evolutionary parameters made using these models. Parameter estimates are contextually dependent on the model used to estimate the parameters and are informative only if the model is a reasonable fit to the data.

A variety of approaches can be used to assess model adequacy, from simple visual examinations to statistical goodness of fit tests. The increased power and interpretability of statistical approaches justify their increased complexity.

A review of existing software packages demonstrates that, when tests for model adequacy are built into software packages by developers, users are more likely to conduct these analyses.

Emergence of size-structured dominance hierarchies through size-dependent feedback

Ian M. Hamilton and Macie D. Benincasa. 2022. Phil. Trans. R. Soc. B 377: 20200449.

Abstract

Size-based dominance hierarchies influence fitness, group size and population dynamics and link dominance structure to evolutionary and ecological outcomes. While larger individuals often gain dominance, social status may influence growth and size in return, resulting in feedbacks among status, growth and size. Here, we present two models evaluating how these feedbacks influence the emergence of size structure in a dominance hierarchy. In the first, size influences competition for food and investment in suppressing growth of groupmates. Stable size differences emerged when suppression was greatest for similarly sized individuals and size had little effect on competition for food. The model predicted size divergence when size strongly affected competition for food. In the second model, we used a dynamic game to solve for optimal investment in growth suppression as a function of size structure. Investment in growth suppression was favoured only when dominants and subordinates were similar in size, generating size ratios different than those expected by chance. Variation in the feedbacks among growth, size and status can explain variation in emergent size structure of dominance hierarchies and its consequences for conflict within groups.

Habitat aridity as a determinant of the trade-off between water conservation and evaporative heat loss in bats

Agustí Muñoz-Garcia, Miriam Ben-Hamo, Shai Pilosof, Joseph B. Williams & Carmi Korine. J Comp Physiol B (2022).

Abstract

The maintenance of water balance in arid environments might represent a formidable challenge for Chiroptera, since they have high surface-to-volume ratios. In deserts, bats conserve water, for example, using daily torpor, but they also might experience episodic heat bouts, when they may need to increase total evaporative water loss (TEWL) to thermoregulate. We hypothesized that in bats, habitat aridity and its variability determine a trade-off between water conservation and thermoregulation via evaporative means. To test this hypothesis, we collated data from the literature of 22 species of bats on TEWL, body temperature and resting metabolic rate, in torpor and euthermy. We also collected data on ambient temperature (Ta) and precipitation of the locations where bats were captured, calculated an aridity index, and built an index of variability of the environment. After correcting for phylogeny, we found that, as aridity and variability of the environment increased, bats had lower values of TEWL, but the rate at which TEWL increases with Ta was higher, supporting our hypothesis. These results suggest that at high Ta there is a trade-off between water conservation and evaporative heat loss in bats. The evolution of physiological mechanisms that allow water conservation and tolerance to conditions of high Ta without access to free water might thus be crucial to explain the distribution of desert bats.

Tolerance of glacial-melt stoneflies (Plecoptera) and morphological responses of chloride cells to stream salinity

Heather Fair, Roman Lanno, Peter C. Smiley Jr. Chemosphere, Volume 293, 2022, 133655, ISSN 0045-6535,

Abstract

Aquatic insects within glacial-melt streams are adapted to low dissolved inorganic ion concentrations. Increases in ion concentrations in glacial-melt streams are predicted with increasing air temperatures, which may impact future aquatic insect survival in these streams. We hypothesized that stonefly (Plecoptera) naiads from glacial-melt streams acclimated to different conductivity would differ in survival, median lethal concentrations, and chloride cell responses to elevated conductivity above that expected in our study streams. We conducted field bioassays in remote glacial-melt streams in southwestern China in 2015 and exposed representative stonefly naiads (Chloroperlidae, Nemouridae, Taeniopterygidae) from stream sites differing in conductivity to experimental conductivity ranging from 11 to 20,486 μS/cm for up to 216 h. We examined survivorship, calculated 96-h median lethal concentrations, and measured chloride cell responses with scanning electron microscopy. Chloroperlidae survival after 120 and 216 h did not differ (P > 0.05) among conductivity treatments. The combined Nemouridae/Taeniopterygidae survival after 120 and 216 h was the least (P < 0.05) in conductivity treatments >16,349 μS/cm. Taeniopterygidae survival after 120 h was also the least (P < 0.05) in conductivity treatments >16,349 μS/cm. The 96-h median lethal concentrations did not differ (P > 0.05) between the combined Nemouridae/Taeniopterygidae group (2306 μS/cm) and Taeniopterigydae (2002 μS/cm) and were lower (P < 0.05) than the 96-h median lethal concentration for Chloroperlidae (8167 μS/cm). Chloroperlidae caviform cell number, density, and area decreased (P < 0.05) with increasing conductivity. Taeniopterygidae caviform cell count decreased (P < 0.05) with increasing conductivity, but cell density and area did not. Chloroperlidae and Taeniopterygidae coniform cell characteristics and Nemouridae bulbiform cell characteristics were not affected by conductivity. Our results suggest that Chloroperlidae, Nemouridae, and Taeniopterygidae from glacial-melt streams in China may be able to tolerate moderate increases in conductivity (i.e., 100 to 200 μS/cm).