Marine species turnover but not richness, peaks at the Equator

Chaudhary, Chhaya; Costello, Mark J.

doi:10.1016/j.pocean.2022.102941

Cited by 5 publications

(3 citation statements)

References 72 publications

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“…Latitudinal diversity gradients (LDGs) integrate over the local and regional patterns where species have evolved and survived on both ecological and evolutionary time scales ( Ekman, 1953 ; Gaston, 2000 ; Willig, Kaufman & Stevens, 2003 ; Pontarp et al, 2019 ). In contrast to expectations that species richness decreases from the equator to the poles, recent studies have shown that the LDG of marine taxa are bimodal with a dip at or near the equator ( Powell, Beresford & Colaianne, 2012 ; Chaudhary, 2019 ; Chaudhary, Saeedi & Costello, 2016 , 2017 ; Chaudhary & Costello, 2023 ; Arfianti & Costello, 2020 ; Lin et al, 2021 ). This was not the case during the last glacial maximum ( Yasuhara et al, 2020 ), and dip has been deepening faster in concert with recent climate change ( Chaudhary et al, 2021 ), indicating that the LDG in terms of species richness is related to temperature ( Lin et al, 2021 ).…”

Section: Introductioncontrasting

confidence: 63%

Body size and trophic level increase with latitude, and decrease in the deep-sea and Antarctica, for marine fish species

Lin,

Costello

2023

PeerJ

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The functional traits of species depend both on species’ evolutionary characteristics and their local environmental conditions and opportunities. The temperature-size rule (TSR), gill-oxygen limitation theory (GOLT), and temperature constraint hypothesis (TCH) have been proposed to explain the gradients of body size and trophic level of marine species. However, how functional traits vary both with latitude and depth have not been quantified at a global scale for any marine taxon. We compared the latitudinal gradients of trophic level and maximum body size of 5,619 marine fish from modelled species ranges, based on (1) three body size ranges, <30, 30–100, and >100 cm, and (2) four trophic levels, <2.20, 2.20–2.80, 2.81–3.70, >3.70. These were parsed into 5° latitudinal intervals in four depth zones: whole water column, 0–200, 201–1,000, and 1,001–6,000 m. We described the relationship between latitudinal gradients of functional traits and salinity, sea surface and near seabed temperatures, and dissolved oxygen. We found mean body sizes and mean trophic levels of marine fish were smaller and lower in the warmer latitudes, and larger and higher respectively in the high latitudes except for the Southern Ocean (Antarctica). Fish species with trophic levels ≤2.80 were dominant in warmer and absent in colder environments. We attribute these differences in body size and trophic level between polar regions to the greater environmental heterogeneity of the Arctic compared to Antarctica. We suggest that fish species’ mean maximum body size declined with depth because of decreased dissolved oxygen. These results support the TSR, GOLT and TCH hypotheses respectively. Thus, at the global scale, temperature and oxygen are primary factors affecting marine fishes’ biogeography and biological traits.

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Section: Introductioncontrasting

confidence: 63%

Body size and trophic level increase with latitude, and decrease in the deep-sea and Antarctica, for marine fish species

Lin,

Costello

2023

PeerJ

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“…Using the same dataset as the present study, Lin et al (2021) found that species richness of marine fishes decreased when the mean annual temperature was greater than 25 °C. Previous studies similarly indicated that some tropical species cannot tolerate present temperatures at the equator, and they move into subtropical latitudes in concert with global warming ( Garciá Molinos et al, 2016 ; Chaudhary, 2019 ; Yasuhara et al, 2020 ; Chaudhary et al, 2021 ; Chaudhary & Costello, 2023 ). Furthermore, species richness across all taxa, including pelagic fish, declines above 20 °C, except for reef fish where it peaks at 25 °C ( Chaudhary et al, 2021 ).…”

Section: Discussionmentioning

confidence: 95%

“…Until recently, the literature presented the typical LDG to be a decrease in species richness from the equator to the poles. However, present LDGs of marine species are now recognized to be bimodal with a dip at or near the equator ( Powell, Beresford & Colaianne, 2012 ; Chaudhary, Saeedi & Costello, 2016 ; Chaudhary et al, 2021 ; Chaudhary & Costello, 2023 ; Arfianti & Costello, 2020 ; Lin et al, 2021 ). This dip was absent during the last glaciation ( Yasuhara et al, 2020 ) and has been deepening with climate change since the 1950s ( Chaudhary et al, 2021 ).…”

Section: Introductionmentioning

confidence: 99%

Numbers of fish species, higher taxa, and phylogenetic similarity decrease with latitude and depth, and deep-sea assemblages are unique

Lin,

Wright,

Costello

2023

PeerJ

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Species richness has been found to increase from the poles to the tropics but with a small dip near the equator over all marine fishes. Phylogenetic diversity measures offer an alternative perspective on biodiversity linked to evolutionary history. If phylogenetic diversity is standardized for species richness, then it may indicate places with relatively high genetic diversity. Latitudes and depths with both high species and phylogenetic diversity would be a priority for conservation. We compared latitudinal and depth gradients of species richness, and three measures of phylogenetic diversity, namely average phylogenetic diversity (AvPD), the sum of the higher taxonomic levels (STL) and the sum of the higher taxonomic levels divided by the number of species (STL/spp) for modelled ranges of 5,619 marine fish species. We distinguished all, bony and cartilaginous fish groups and four depth zones namely: whole water column; 0 –200 m; 201–1,000 m; and 1,001–6,000 m; at 5° latitudinal intervals from 75°S to 75°N, and at 100 m depth intervals from 0 m to 3,500 m. Species richness and higher taxonomic richness (STL) were higher in the tropics and subtropics with a small dip at the equator, and were significantly correlated among fish groups and depth zones. Species assemblages had closer phylogenetic relationships (lower AvPD and STL/spp) in warmer (low latitudes and shallow water) than colder environments (high latitudes and deep sea). This supports the hypothesis that warmer shallow latitudes and depths have had higher rates of evolution across a range of higher taxa. We also found distinct assemblages of species in different depth zones such that deeper sea species are not simply a subset of shallow assemblages. Thus, conservation needs to be representative of all latitudes and depth zones to encompass global biodiversity.

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