TY - JOUR

T1 - Single-specimen systematics resolves the phylogeny and diversity conundrum of enigmatic crustacean y-larvae

AU - Dreyer, Niklas

AU - Palero, Ferran

AU - Grygier, Mark J.

AU - Chan, Benny K. K.

AU - Olesen, Jørgen

N1 - Publisher Copyright: © 2023

PY - 2023

Y1 - 2023

N2 - Resolving the evolutionary history of organisms is a major goal in biology. Yet for some taxa the diversity, phylogeny, and even adult stages remain unknown. The enigmatic crustacean “y-larvae” (Facetotecta) are one particularly striking example. Here, we use extensive video-imaging and single-specimen molecular sequencing of >200 y-larval specimens to comprehensively explore for the first time their evolutionary history and diversity. This integrative approach revealed five major clades of Facetotecta, four of which encompass a considerable larval diversity. Whereas morphological analyses recognized 35 y-naupliar “morphospecies”, molecular species-delimitation analyses suggested the existence of between 88 and 127 species. The phenotypic and genetic diversity between the morphospecies suggests that a more elaborate classification than the current one-genus approach is needed. Morphology and molecular data were highly congruent at shallower phylogenetic levels, but no morphological synapomorphies could be unambiguously identified for major clades, which mostly comprise both planktotrophic and lecithotrophic y-nauplii. We argue that lecithotrophy arose several times independently whereas planktotrophic y-nauplii, which are structurally more similar across clades, most likely display the ancestral feeding mode of Facetotecta. We document a remarkably complex and highly diverse phylogenetic backbone for a taxon of larval marine crustaceans, the full life cycle of which remains a mystery.

AB - Resolving the evolutionary history of organisms is a major goal in biology. Yet for some taxa the diversity, phylogeny, and even adult stages remain unknown. The enigmatic crustacean “y-larvae” (Facetotecta) are one particularly striking example. Here, we use extensive video-imaging and single-specimen molecular sequencing of >200 y-larval specimens to comprehensively explore for the first time their evolutionary history and diversity. This integrative approach revealed five major clades of Facetotecta, four of which encompass a considerable larval diversity. Whereas morphological analyses recognized 35 y-naupliar “morphospecies”, molecular species-delimitation analyses suggested the existence of between 88 and 127 species. The phenotypic and genetic diversity between the morphospecies suggests that a more elaborate classification than the current one-genus approach is needed. Morphology and molecular data were highly congruent at shallower phylogenetic levels, but no morphological synapomorphies could be unambiguously identified for major clades, which mostly comprise both planktotrophic and lecithotrophic y-nauplii. We argue that lecithotrophy arose several times independently whereas planktotrophic y-nauplii, which are structurally more similar across clades, most likely display the ancestral feeding mode of Facetotecta. We document a remarkably complex and highly diverse phylogenetic backbone for a taxon of larval marine crustaceans, the full life cycle of which remains a mystery.

KW - Facetotecta

KW - Larval evolution

KW - Larval systematics

KW - Phylogeny estimation

U2 - 10.1016/j.ympev.2023.107780

DO - 10.1016/j.ympev.2023.107780

M3 - Journal article

C2 - 37031710

AN - SCOPUS:85158887755

VL - 184

JO - Molecular Phylogenetics and Evolution

JF - Molecular Phylogenetics and Evolution

SN - 1055-7903

M1 - 107780

ER -