Alan A. Myers

Spatial and temporal variation in settlement and recruitment of the intertidal barnacle Semibalanus balanoides (L.) (Crustacea : Cirripedia) over a European scale

Variation in the level of settlement and recruitment in the intertidal barnacle Semibalanus balanoides was studied using a hierarchical sampling programme. The effect of three spatial scales, 10s of metres (sites), 1000s of metres (shores) and 100s of kilometres (locations), was determined. The largest spatial scale represented the distance between four widely separated locations, Sweden, the Isle of Man, SW Ireland and SW England, covering a large part of the range of S. balanoides in Europe. Temporal variation was determined by comparison between two years, 1997 and 1998. The settlement period of S. balanoides varied in length and timing, being earlier and shorter at the most northerly location, Sweden. The duration of settlement showed little difference among shores within locations, but the pattern of settlement did vary. Estimates of total settlement throughout the settlement period and of recruitment at the end of this period both showed substantial variation among locations which was dependent on the year of study. There was little consistency in the ranking of locations between the two years. Recruitment showed significant variation at the lower spatial scales of shore and site. In addition, examination of variance components showed a high degree of variation between replicates within sites in 1997. There was a significant relationship between settlement and recruitment at three of the four locations. Across all locations variation in settlement explained between 29 and 99% of variation in recruitment. However, locations showed distinct differences in the level of post-settlement survival.

A PHYLOGENY AND A NEW CLASSIFICATION OF THE COROPHIIDEA LEACH, 1814 (AMPHIPODA)

Abstract Based on a phylogenetic analysis of 104 genera and 156 species of corophiidean amphipods, we present a new phylogeny and higher-level classification for the suborder Corophiidea Leach, 1814. The phylogeny divides the corophiideans into two infraorders, the Corophiida and the Caprellida, based on a hypothesis of the evolution of different feeding strategies. Members of the Corophiida are derived from bottom-feeding detritivores, whereas members of the Caprellida are derived from ancestors that fed on material suspended in the water column. Within the Corophiida there are unspecialized clades such as the aoroids, whose members are mainly detrital feeders, as well as specialized forms feeding on living algae (family Ampithoidae) and on wood (superfamily Cheluroidea). In the Caprellida, members of the podocerid and caprellid clades often climb organisms such as hydroids in order to get their antennae as far up in the water column as possible to suspension-feed, whereas ischyrocerins build nests and then suspension-feed. Specialized forms include cyamids that attach to whales where they “feed on whale skin.” Barnard and Karaman (1984) divided the Corophiidea into two superfamilies (Corophiidea and Caprelloidea) within which were nine families. The classification presented here includes those two infraorders, with 11 superfamilies, 21 families, 13 subfamilies, and 5 tribes.

Using historical data to detect temporal changes in the abundances of intertidal species on Irish shores

An historical data set, collected in 1958 by Southward and Crisp, was used as a baseline for detecting change in the abundances of species in the rocky intertidal of Ireland. In 2003, the abundances of each of 27 species was assessed using the same methodologies (ACFOR [which stands for the categories: abundant, common, frequent, occasional and rare] abundance scales) at 63 shores examined in the historical study. Comparison of the ACFOR data over a 45-year period, between the historical survey and re-survey,showed statistically signi¢cant changes in the abundances of 12 of the 27 species examined. Two species(one classed as northern and one introduced) increased signi¢cantly in abundance while ten species (¢ve classed as northern, one classed as southern and four broadly distributed) decreased in abundance. The possible reasons for the changes in species abundances were assessed not only in the context of anthropogenic eiects, such as climate change and commercial exploitation, but also of operator error. The error or diierences recorded among operators (i.e. research scientists) when assessing species abundance using ACFOR categories was quanti¢ed on four shores. Signi¢cant change detected in three of the 12 species fell within the margin of operator error. This eiect of operator may have also contributed to the results of no change in the other 15 species between the two census periods. It was not possible to determine the eiect of operator on our results, which can increase the occurrence of a false positive (Type 1) or of a false negative (Type 2) outcome.

Artificial substrates as a means of monitoring rocky shore cryptofauna

Two types of artificial substrate (nylon pan-scourers) have been shown to be highly efficient collectors of cryptofauna on rocky shores. The communities which develop in them are closely similar to those which develop in naturally occurring red algal turfs in Bantry Bay. The physical structure of the red algae appears to be the prime factor in determining the development of populations of most of the cryptofaunal species studied. In monitoring protocols artificial substrates of the types described here can be substituted for naturally occurring red algae in studies on shore cryptofauna obviating the necessity for destructive sampling of algae and facilitating statistical analysis by providing a standard ‘unit’ of substrate for comparative purposes. Furthermore, recruitment intensity of two species of gastropod has been shown to be similar in the artificial substrates to that in natural turfs

A Phylogeny and a New Classification of the Corophiidea (Amphipoda)

Based on a phylogenetic analysis of 104 genera and 156 species of corophiidean amphipods, we present a new phylogeny and higher-level classification for the suborder Corophiidea Leach, 1814. The phylogeny divides the corophiideans into two infraorders, the Corophiida and the Caprellida, based on a hypothesis of the evolution of different feeding strategies. Members of the Corophiida are derived from bottomfeeding detritivores, whereas members of the Caprellida are derived from ancestors that fed on material suspended in the water column. Within the Corophiida there are unspecialized clades such as the aoroids, whose members are mainly detrital feeders, as well as specialized forms feeding on living algae (family Ampithoidae) and on wood (superfamily Cheluroidea). In the Caprellida, members of the podocerid and caprellid clades often climb organisms such as hydroids in order to get their antennae as far up in the water column as possible to suspension-feed, whereas ischyrocerins build nests and then suspension-feed. Specialized forms include cyamids that attach to whales where they ‘‘feed on whale skin.’’ Barnard and Karaman (1984) divided the Corophiidea into two superfamilies (Corophiidea and Caprelloidea) within which were nine families. The classification presented here includes those two infraorders, with 11 superfamilies, 21 families, 13 subfamilies, and 5 tribes. Barnard and Karaman (1984) proposed an untested scheme, which placed the infraorders Caprellida (as Caprelloidea) and Corophiida (as Corophioidea) in the suborder Corophiidea Leach (1814). It should be noted that Stebbing (1906) attributed the Corophiidae to Dana (1849), but this is in error. Leach (1814: 405) erected the Corophiidae (as the family Corophiini) where it has page placement priority over the family Caprellini. This error has since been perpetuated by all authors, including Barnard and Karaman (1984, 1991). Within the corophiideans (sensu lato), the internal phylogenetic relationships have always been uncertain. Barnard and Karaman (1991) attempted no phylogenetic classification of their infraorder Corophiida, commenting that ‘‘the practical identification of family or subfamily groups in this conglomerate is very difficult.’’ Laubitz (1993) and Takeuchi (1993) both proposed untested schemes for the Caprelloidea (in the traditional sense). The lack of clarity that surrounds the relationships of this group is not unique within the Amphipoda, but it has been particularly intractable in the corophiideans. We should not, however, be surprised. The punctuated nature of evolution may always result in low-resolution trees, which are based on extant taxa. Whenever a new innovation occurs during the course of evolution, it is probably followed by explosive adaptive radiation as the innovator invades new niches, further developing and adapting its innovation. Most of the descendants of the early innovator will fail and become extinct; only a few will succeed to form new clades. Such bursts of evolutionary innovation make it difficult, if not impossible, to distinguish the dichotomous nature of character-state acquisition by examining only extant taxa. Interpretation of phylogeny through a cladistic study of living species will result in trees with unresolvable polychotomies. The precision of a cladistic analysis will vary with the hierarchical taxonomic level analyzed (and hence to temporal scale). Analyses of species groups should generally yield rather clear relationships, because there are fewer missing links, but the clarity will decrease, perhaps exponentially as earlier and earlier relationships are investigated. This means that we should, perhaps, be rather skeptical of a tree pertaining to family relationships that purports to be fully resolved. The best we can expect, and for the present with which 443 JOURNAL OF CRUSTACEAN BIOLOGY, 23(2): 443–485, 2003

How did Hawaii accumulate its biota? A test from the Amphipoda

An analysis was carried out of the distributions of Hawaiian gammaridean Amphipoda of the families Aoridae and Melitidae to determine (a) whether there was a correlation between perceived dispersal potential and extent of endemicity, and (b) whether the biogeographic affinities of the two families differed. A new application of PAE is developed and applied to all families of gammaridean Amphipoda from the Indo-Pacific and Caribbean to attempt to interpret the history of space occupancy by lineages. Resulting PAE cladograms suggest a shift in the biogeographic relationships of Hawaii from the eastern Pacific and Caribbean in the past to the south west and central Pacific in modem times.

Brooding in the intertidal barnacles Chthamalus stellatus (Poli) and Chthalamus montagui Southward in south-western Ireland

At Lough Hyne Marine Nature Reserve, western Cork, Ireland, the intertidal barnacles Chthamalus stellatus (Poli) and Chthamalus montagui Southward were shown to be capable of breeding in their first year after settlement. In C. montagui, zero, one or two broods and in C. stellatus, zero, one, two or in a single case three broods were produced in the first summer. Whether or not barnacles brood in their first year is probably due to a combination of the time since settlement and size attained. In their second year after settlement, both species are multiple brooders, producing two broods during the summer season.

Recruitment, immigration and population structure of two coexisting limpet species in mid-shore tidepools, on the west Coast of Ireland

Abstract Patellid limpets are common occupants of mid-shore tidepools on northern European shores, but their tidepool population structures have not been examined in detail. A series of mid-shore tidepools on Clare Island, Western Ireland were cleared of all Patella ulyssiponensis , Gmelin and P. vulgata L., in each of three years. A subset of these pools was subsequently recleared at monthly intervals, to determine juvenile recruitment to the pools and the rates of adult immigration. P. vulgata juveniles ( P. ulyssiponensis , but there was a steady decline of the P. vulgata recruits over time. The majority of limpets in the largest size class (>20 mm) were P. ulyssiponensis . No difference between the two species was observed in the immigration rates of the adults to the pools, but it is suggested that while P. ulyssiponensis remains in the pools, P. vulgata uses this microhabitat solely as a nursery ground, migrating from the pools as the animals increase in size, to give the observed pattern in population structure.

Turnover of transient species as a contributor to the richness of a stable amphipod (Crustacea) fauna in a sea inlet

Abstract Colonization and turnover of amphipod (Crustacea) species was studied on experimental plastic mesh pads for 12 months in the marine subtidal. The species colonization curve, ratio of colonization to decolonization rates, and stability of turnover, indicated that the amphipod fauna was at equilibrium after 4 months. At equilibrium, this fauna could be categorised as residents (almost always present) and transients (rare in numbers of individuals and frequency of occurrence in time), with an intermediate group of temporary residents. Most of the species turnover and the seasonal increase in the number of species on the pads was attributable to transients. Transients represented 33–44% of the number of species observed in each of three time-series of pads, so a significant part of the species richness was dependent on the dispersal of amphipods from different nearby habitats. Considering their rarity, it is unlikely that these transient species played any functional role in the observed community. However, they may become residents, should environmental conditions change in the future. These results suggest that high numbers of rare species may reflect not only a habitats intrinsic richness, but also the distance to different habitats where transients originate.

Mussel fouling on the Celtic Sea Kinsale Field gas platforms

Abstract Fouling was investigated on Marathon Kinsale Field Alpha and Bravo platforms in the Celtic Sea between June 1978 and June 1981. In shallow depths, algae dominated, chiefly Polysiphonia brodiaei and Ulva lactuca. Mussels formed the dominant fouling organism between 6 and 20 m depth, below which were zones of Metridium senile and Alcyonium digitatum, serpulids and the deep water barnacle Balanus hameri. In September 1979 mussels exceeded 2500 m−2 with a modal length of 42 mm. By June 1981, modal length had increased to 67 mm at −4 m and 73 mm at −18 m (maximum size 97 mm). Populations on Bravo were similar. Comparison is made with growth rates on North Sea platforms. On Alpha, percentage cover m−2 in March 1980 was much greater at −4 m than at −18 m, but mean thickness was similar. At −18 m mussels were a heavier fouler on Bravo than Alpha. On Alpha mussel weight did not show a linear relationship with percentage cover.