Matthew H. Dick

Molecular phylogeny and phylogeography of free-living Bryozoa (Cupuladriidae) from both sides of the Isthmus of Panama

Genetic data were used to identify Recent species of free-living bryozoans (Cupuladriidae) from both sides of the Isthmus of Panama, and to examine their phylogenetic relationships, species richness, and population structures. An approximately 480bp fragment of the 16S mitochondrial rRNA gene was sequenced from 182 individuals from Panama, the Gulf of Mexico, and El Salvador. Ten haplotype groups (Cupuladria 4, 5, and 6; Discoporella 1, 2, 3A, 3B, 3C, 7, and 8) were identified. Genetic distances between haplotype groups (3.2-26.5%; K2P+Gamma) were 1-2 orders of magnitude greater than within groups (0.1-1.4%). Seven of the haplotype groups represent morphologically distinct species; Discoporellas 3A-C appear to be cryptic species. Phylogenetic analyses identified two pairs of transisthmian sister clades. An average divergence rate derived from other taxa suggests that Cupuladrias 4 and 5 diverged approximately 7Ma, a Discoporella 7 clade diverged from a 3A-C clade approximately 11Ma, and the 3A-C clade radiated approximately 6-4Ma; these events all predated final closure of the isthmus? 3Ma. The Caribbean side of the isthmus, with 5 species, is only marginally richer in cupuladriids than the Pacific side, with 4, but has greater phylogenetic depth. The Caribbean retains lineages stemming from a New World Miocene radiation that are not represented in the eastern Pacific; extant eastern Pacific cupuladriids share most recent common ancestry with only two of the Caribbean lineages. Species in the eastern Pacific tend to show shallow population structures, with high levels of gene flow between geographically separate populations, whereas Caribbean species tend to show deeper populations structures, with indications of restricted gene flow between Bocas del Toro/Gulf of Mosquitos and Costa Arriba/San Blas. The population structures derive from Pleistocene histories and may be of limited value in interpreting the macroevolutionary pattern, as our results provide no evidence of speciation on either side of the isthmus following closure in the late Pliocene.

Epibionts of the Tanner Crab Chionoecetes Bairdi in the Region of Kodiak Island, Alaska

ABSTRACT We examined the epibionts on 98 legal male Tanner crabs (Chionoecetes bairdi) of varying, known shell ages, which were tagged in the region of Kodiak Island, Alaska, and recovered in the commercial fishery. We found 39 species or collective taxa of organisms on C. bairdi, a conservative estimate of the number of species involved. Seven species or collective taxa occurred on the exposed outer surface of ≥50% of all crabs examined: Alcyonidium sp., Balanus spp., a tube-dwelling amphipod, Spirorbis spp., Serpula spp., a lichenoporid bryozoan, and the fungus Trichomaris invadens.At least 12 species occurred in the branchial chamber. Of these, Triticella sp., Alcyonidiumsp., and mucoid-tube polychaetes were found in ≥50% of 25 branchial cavities examined. Three species (Triticella sp.; a small, white flatworm; and Hiatella arctica) were found only in the branchial chamber. Our data showed trends of increasing frequency of occurrence and increasing mean number of epibionts with increasing shell age. Crab-shell age was a significant factor in determining the number of epibiotic species on crabs; the area of origin was not a significant factor. Epibionts are likely to be of limited use as a management tool, because of difficulties in accurately assessing the age composition of commercial samples and the likelihood of temporal and geographic variation in recruitment of epibiont organisms. However, epibionts are probably a significant factor in the population dynamics of C. bairdi and, hence, worthy of further investigation.

Diversity and taxonomy of intertidal Bryozoa (Cheilostomata) at Akkeshi Bay, Hokkaido, Japan

We found 39 cheilostome species among more than 7000 specimens collected at 10 intertidal sites in rocky habitats along the shore of Akkeshi Bay, eastern Hokkaido Island, Japan. These species are herein described in detail and illustrated by scanning electron microscopy. Nine species (23% of total) are described as new (Electra asiatica, Callopora sarae, Conopeum nakanosum, Cauloramphus cryptoarmatus, Cauloramphus multispinosus, Cauloramphus niger, Stomachetosella decorata, Microporella luellae, and Celleporina minima), and 21 species (54%) are reported for the first time from Japan. Species richness ranged from eight to 29 species per study site. A TWINSPAN analysis showed the species fell into nine groups defined by the local pattern of distribution. A cluster analysis of study sites based on similarity of species composition showed three faunistic groups distributed geographically: in Akkeshi Lake, along the eastern‐central shore of the bay, and at the mouth of the bay. Species richness in estuarine Akkeshi Lake was low, with a species composition very different from the outer bay. Most cheilostomes were found on rock and shell substrata, but uncommonly occurred on concrete walls, algae, hydroids, tubes of polychaetes, other bryozoans, and anthropogenic debris. Of the 39 species found, 33 (85%) contained embryos during the collecting periods, 2–7 June and 3–6 July 2004. The biogeographical composition of intertidal cheilostomes at Akkeshi Bay included species with Arctic‐Boreal (28%), Boreal (59%), and Boreal‐Subtropical (13%) distributions. The overall species richness of intertidal cheilostomes was two‐thirds that documented intertidally in a comparable study at Kodiak, Alaska, a locality 15° higher in latitude. We attribute the lower richness at Akkeshi to differences in the nearshore marine environment between the two localities.

NEOGENE CUPULADRIIDAE OF TROPICAL AMERICA. I: TAXONOMY OF RECENT CUPULADRIA FROM OPPOSITE SIDES OF THE ISTHMUS OF PANAMA

Abstract We used up to 30 morphological characters to discriminate and describe species of the genus Discoporella based on complete colony specimens collected from both coasts of the Isthmus of Panama. The characters included zooidal characters and colony-level characters such as colony size and basal granule density. Species were classified by a series of multivariate cluster and linear discriminant analyses until the majority of specimens were assigned to their putative species with high confidence. In the first phase of the analyses, the colonies were grouped by ocean (Caribbean versus eastern Pacific), discriminated predominantly by colony size and basal granule density, characters that might reflect ecophenotypic responses to different conditions in primary productivity and predation between the two oceans. Further analyses of these two groups separately resulted in the discrimination of seven species. Five new species from the Caribbean (D. scutella, D. peltifera, D. bocasdeltoroensis, D. terminata and D. triangula), and two from the eastern Pacific (D. marcusorum and D. cookae). Of these, D. cookae had been identified previously as D. umbellata, a species once considered cosmopolitan, with a range spanning the Caribbean and eastern Pacific coasts of America. With the exception of one genetically defined clade represented by only two specimens, the correspondence of classification between groups discriminated morphometrically by separate step-wise multivariate analyses and those detected by a previous genetic analysis, ranged from 91% to 100%. In analyses of all specimens combined or separated by ocean, but using the total number of characters, 20% to 30% of the specimens could not be distinguished morphometrically from extremely similar sympatric species or cognate (“geminate”) species from the opposite ocean. Diversity was higher in the Caribbean compared to the eastern Pacific, which reflects a similar pattern recently described for the genus Cupuladria from the same region.

Division of labor and recurrent evolution of polymorphisms in a group of colonial animals

Rendering developmental and ecological processes into macroevolutionary events and trends has proved to be a difficult undertaking, not least because processes and outcomes occur at different scales. Here we attempt to integrate comparative analyses that bear on this problem, drawing from a system that has seldom been used in this way: the co-occurrence of alternate phenotypes within genetic individuals, and repeated evolution of distinct categories of these phenotypes. In cheilostome bryozoans, zooid polymorphs (avicularia) and some skeletal structures (several frontal shield types and brood chambers) that evolved from polymorphs have arisen convergently at different times in evolutionary history, apparently reflecting evolvability inherent in modular organization of their colonial bodies. We suggest that division of labor evident in the morphology and functional capacity of polymorphs and other structural modules likely evolved, at least in part, in response to the persistent, diffuse selective influence of predation by small motile invertebrate epibionts.

The origin of ascophoran bryozoans was historically contingent but likely

The degree to which evolutionary outcomes are historically contingent remains unresolved, with studies at different levels of the biological hierarchy reaching different conclusions. Here we examine historical contingency in the origin of two evolutionary novelties in bryozoans, a phylum of colonial animals whose fossil record is as complete as that of any major group. In cheilostomes, the dominant living bryozoans, key innovations were the costal shield and ascus, which first appeared in the Cretaceous 85–95 Myr ago. We establish the parallel origin of these structures less than 12 Myr ago in an extant bryozoan genus, Cauloramphus, with transitional stages remarkably similar to those inferred for a Cretaceous clade. By one measure, long lag times in the first origins of costal shield and ascus suggest a high degree of historical contingency. This, however, does not equate with dependence on a narrow set of initial conditions or a low probability of evolution. More than one set of initial conditions may lead to an evolutionary outcome, and alternative sets are not entirely independent. We argue that, although historically contingent, the origin of ascus and costal shield was highly likely with sufficient possibilities afforded by time.

The Internal-Brooding Apparatus in the Bryozoan Genus Cauloramphus (Cheilostomata: Calloporidae) and Its Inferred Homology to Ovicells

Abstract We studied by SEM the external morphology of the ooecium in eight bryozoans of the genus Cauloramphus Norman, 1903 (Cheilostomata, Calloporidae): C. spinifer, C. variegatus, C. magnus, C. multiavicularia, C. tortilis, C. cryptoarmatus, C. niger, and C. multispinosus, and by sectioning and light microscopy the anatomy of the brooding apparatus of C. spinifer, C. cryptoarmatus, and C. niger. These species all have a brood sac, formed by invagination of the non-calcified distal body wall of the maternal zooid, located in the distal half of the maternal (egg-producing) autozooid, and a vestigial, maternally budded kenozooidal ooecium. The brood sac comprises a main chamber and a long passage (neck) opening externally independently of the introvert. The non-calcified portion of the maternal distal wall between the neck and tip of the zooidal operculum is involved in closing and opening the brood sac, and contains both musculature and a reduced sclerite that suggest homology with the ooecial vesicle of a hyperstomial ovicell. We interpret the brooding apparatus in Cauloramphus as a highly modified form of cheilostome hyperstomial ovicell, as both types share 1) a brood chamber bounded by 2) the ooecium and 3) a component of the distal wall of the maternal zooid. We discuss Cauloramphus as a hypothetical penultimate stage in ovicell reduction in calloporid bryozoans. We suggest that the internal-brooding genus Gontarella, of uncertain taxonomic affinities, is actually a calloporid and represents the ultimate stage in which no trace of the ooecium remains. Internal brooding apparently evolved several times independently within the Calloporidae.

Cribrimorph and Other Cauloramphus Species (Bryozoa: Cheilostomata) from the Northwestern Pacific

We provide original descriptions for nine new species in the cheilostome bryozoan genus Cauloramphus (C. gracilis, C. Ordinarius, C. amphidisjunctus, C. cheliferoides, C. oshurkovi, C. infensus, C. parvus, C. peltatus, and C. ascofer) and a redescription of C. disjunctus Canu and Bassler, 1929. We delineate a group of eight species, here termed the ‘C. disjunctus clade,’ that have the opesial spine joints calcified to a greater or lesser extent in mature zooids; most also have paired, hypertrophied avicularia. This group includes C. amphidisjunctus, C. cheliferoides, C. infensus, C. parvus, C. peltatus, and C. ascofer in the Aleutian Islands, Alaska; C. oshurkovi in the Commander Islands; and C. disjunctus in Japan. High levels of apparent endemism in two unrelated bryozoan genera (Cauloramphus and Monoporella), and geographical population differentiation in C. ascofer indicating ongoing allopatric speciation, suggest high speciation rates for deep benthic bryozoans in the western Aleutians. A phylogenetic hypothesis for the C. disjunctus clade indicates that populations of Cauloramphus dispersed between the Aleutians and Asia on at least three separate occasions, and that the polarity of at least two of these dispersal events was from the Aleutians to Asia.

Birds of the Kilbuck and Ahklun Mountain Region, Alaska

Summary of the birds of the Kilbuck and Ahklun Mountain region, including geographical distribution, population status, migration habits, nesting habitat, and zoogeography.

Unexpectedly High Diversity of Monoporella (Bryozoa: Cheilostomata) in the Aleutian Islands, Alaska: Taxonomy and Distribution of Six New Species

Abstract The cheilostome bryozoan genus Monoporella is poorly resolved taxonomically; only four Recent species have been formally described, though several undescribed species have been reported in the literature. The literature indicates no more than five species in the genus occurring in any local region of the world, with one to three species in most regions where the genus has been reported. I examined bryozoans from 52 trawl catches in the western and western-central Aleutian Islands, Alaska, and found specimens of Monoporella in 12 of these samples. Study of these specimens by scanning electron microscopy (SEM) revealed six new species that are described herein: M. flexibila, M. elongata, M. gigantea, M. ellefsoni, M. seastormi, and M. aleutica. Two of the species have erect colony morphologies, a condition not previously reported in Monoporella. The species diversity of Monoporella appears to be greater in the Aleutians than in any other part of the world adequately surveyed. I discuss whether this apparent high diversity is an artifact due to insufficient sampling in the deep shelf zone, and present two hypotheses to explain this high diversity should it prove not to be an artifact: 1) the present high local diversity represents a relict of past high diversity occurring broadly around the North Pacific rim; and 2) a local radiation of Monoporella occurred in the Aleutian archipelago.