Abstract:During the past decade, a large number of multi-gene analyses aimed at resolving the phylogenetic relationships within Decapoda. However relationships among families, and even among sub-families, remain poorly defined. Most analyses used an incomplete and opportunistic sampling of species, but also an incomplete and opportunistic gene selection among those available for Decapoda. Here we test in the Caridea if improving the taxonomic coverage following the hierarchical scheme of the classification, as it is cu… Show more
“…The non-monophyly of Pasiphaeidae has been suspected hitherto 31 , with a recent recalibration of the constituent genera 32 . Despite considerable progress towards resolving the problematic phylogeny of Hippolytidae sensu lato 30 , further studies found additional polyphyly 33 , consistent in generic scope with the present analysis. The division of the older concept of Oplophoridae into two families 34 has remained controversial 35 , with one genus— Systellaspis —occupying an intermediate position between two families, as in the present analysis.Fig.…”
Understanding the processes that shaped the strikingly irregular distribution of species richness across the Tree of Life is a major research agenda. Changes in ecology may go some way to explain the often strongly asymmetrical fates of sister clades, and we test this in the caridean shrimps. First appearing in the Lower Jurassic, there are now ~3500 species worldwide. Carideans experienced several independent transitions to freshwater from marine habitats, while many of the marine species have also evolved a symbiotic lifestyle. Here we use diversification rate analyses to test whether these ecological traits promote or inhibit diversity within a phylogenetic framework. We demonstrate that speciation rates are more than twice as high in freshwater clades, whilst symbiotic ecologies are associated with lower speciation rates. These lower rates amongst symbiotic species are of concern given that symbioses often occur in some of the most diverse, delicately balanced and threatened marine ecosystems.
“…The non-monophyly of Pasiphaeidae has been suspected hitherto 31 , with a recent recalibration of the constituent genera 32 . Despite considerable progress towards resolving the problematic phylogeny of Hippolytidae sensu lato 30 , further studies found additional polyphyly 33 , consistent in generic scope with the present analysis. The division of the older concept of Oplophoridae into two families 34 has remained controversial 35 , with one genus— Systellaspis —occupying an intermediate position between two families, as in the present analysis.Fig.…”
Understanding the processes that shaped the strikingly irregular distribution of species richness across the Tree of Life is a major research agenda. Changes in ecology may go some way to explain the often strongly asymmetrical fates of sister clades, and we test this in the caridean shrimps. First appearing in the Lower Jurassic, there are now ~3500 species worldwide. Carideans experienced several independent transitions to freshwater from marine habitats, while many of the marine species have also evolved a symbiotic lifestyle. Here we use diversification rate analyses to test whether these ecological traits promote or inhibit diversity within a phylogenetic framework. We demonstrate that speciation rates are more than twice as high in freshwater clades, whilst symbiotic ecologies are associated with lower speciation rates. These lower rates amongst symbiotic species are of concern given that symbioses often occur in some of the most diverse, delicately balanced and threatened marine ecosystems.
“…Shrimp exhibit a stunning variety of claw forms (Figures 1; Figures S1-S4). When claw-joint types for first and second pereopods (hereafter P1 and P2) were mapped onto published phylogenies [13,16,17], we reconstructed five phases to snapping-claw evolution: (1) pivot joint / (2) slip joint / (3) cocking (torquereversal) slip joint / (4) cocking slip joint with cavitation (snap) / (5) cocking pivot joint with cavitation ( Figure 2) (see Table S1 for claw-joint states and closing modes for all taxa; STAR Methods for claw imaging, scoring, and character mapping protocols; Figures SM3-SM9 in Methods S1 for implications of alternate phylogenies; and Ultrafast Closing in Caridean Shrimp Claws: A Novel Cocking Mechanism for biomechanical details). Throughout our discussion, by ''snap'' we mean ''snap with cavitation,'' and we refer to the major claw for taxa with asymmetrical P1 or P2 chelae.…”
Section: Comparative Morphology and Evolutionary History Of Shrimp CLmentioning
How do stunning functional innovations evolve from unspecialized progenitors? This puzzle is particularly acute for ultrafast movements of appendages in arthropods as diverse as shrimps [1], stomatopods [2], insects [3-6], and spiders [7]. For example, the spectacular snapping claws of alpheid shrimps close so fast (∼0.5 ms) that jetted water creates a cavitation bubble and an immensely powerful snap upon bubble collapse [1]. Such extreme movements depend on (1) an energy-storage mechanism (e.g., some kind of spring) and (2) a latching mechanism to release stored energy quickly [8]. Clearly, rapid claw closure must have evolved before the ability to snap, but its evolutionary origins are unknown. Unearthing the functional mechanics of transitional stages is therefore essential to understand how such radical novel abilities arise [9-11]. We reconstructed the evolutionary history of shrimp claw form and function by sampling 114 species from 19 families, including two unrelated families within which snapping evolved independently (Alpheidae and Palaemonidae) [12, 13]. Our comparative analyses, using micro-computed tomography (microCT) and confocal imaging, high-speed video, and kinematic experiments with select 3D-printed scale models, revealed a previously unrecognized "slip joint" in non-snapping shrimp claws. This slip joint facilitated the parallel evolution of a novel energy-storage and cocking mechanism-a torque-reversal joint-an apparent precondition for snapping. Remarkably, these key functional transitions between ancestral (simple pinching) and derived (snapping) claws were achieved by minute differences in joint structure. Therefore, subtle changes in form appear to have facilitated wholly novel functional change in a saltational manner. VIDEO ABSTRACT.
“…Locations are coded as follows: RI for Reunion Island, NC for New Caledonia, FP for French Polynesia and LNI for northern Line Islands. [1] 74 ; [2] 75 ; [3] 76 ; [4] 77 ; [5] 9 ; [6] 78; DS direct submission.…”
Several obligate associate crabs and shrimps species may co-occur and interact within a single coral host, leading to patterns of associations that can provide essential ecological services. However, knowledge of the dynamics of interactions in this system is limited, partly because identifying species involved in the network remains challenging. In this study, we assessed the diversity of the decapods involved in exosymbiotic assemblages for juvenile and adult Pocillopora damicornis types α and β on reefs of New Caledonia and Reunion Island. This approach revealed complex patterns of association at regional and local scales with a prevalence of assemblages involving crab-shrimp partnerships. Furthermore, the distinction of two lineages in the snapping shrimp Alpheus lottini complex, rarely recognized in ecological studies, reveals a key role for cryptic diversity in structuring communities of mutualists. The existence of partnerships between species that occurred more commonly than expected by chance suggests an increased advantage for the host or a better adaptation of associated species to local environmental conditions. The consideration of cryptic diversity helps to accurately describe the complexity of interaction webs for diverse systems such as coral reefs, as well as the functional roles of dominant associated species for the persistence of coral populations.
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