Biogeography of the New Zealand Torrentfish, Cheimarrichthys fosteri (Teleostei: Pinguipedidae): A Distribution Driven Mostly by Ecology and Behaviour

Cheimarrichthys fosteri is an endemic New Zealand freshwater fish that has its closest common ancestry with the blue cod, Parapercis colias, a species found in New Zealand coastal seas. Cheimarrichthys fosteri is amphidromous, and widely distributed around New Zealand. The fact that it has marine-living juvenile has a strong impact on the species' distribution. Upstream/inland penetration in river systems is substantial, and the torrentfish reaches 700m elevation and 289km upstream from the sea. High elevation is typically achieved only at relatively short distances inland, whereas long inland penetration is achieved typically only in low-gradient river systems. The torrentfish is a poor climber, and explicit barriers to upstream migration, such as natural falls and the construction of dams and weirs, limit inland penetration in many river systems. Sparse distribution in some areas, particularly in eastern New Zealand may be due in part to absence or sparseness of riverine gravels. Absence from other areas, such as around Cook and Foveaux straits, the Marlborough Sounds, Fiordland and Stewart and Chatham islands, may result from oceanographic conditions that do not favour return to rivers of the marine-living juveniles. Ecological and behavioural variables relating to the marine life intervals are the predominating factors influencing distribution, and historical biogeographical influences are of minor importance.     

Historical transoceanic dispersal of a freshwater shrimp: the colonization of the South Pacific by the genus Paratya (Atyidae)

Aim To infer the phylogenetic relationships within the freshwater shrimp genus Paratya Miers, 1882 (Atyidae) and to use these data to answer biogeographical questions about the location, timing and form of evolution of this genus in the South Pacific. Location Paratya are spread throughout various freshwater habitats in the western Pacific, with a disjunct northern range in the North Pacific (Japan, Korea, Ryukyu Islands, Siberia) and South Pacific (Australia, New Zealand, New Caledonia, Lord Howe, Norfolk Island). Methods Specimens were obtained from throughout its range. Mitochondrial sequences of cytochrome oxidase subunit I and 16S ribosomal DNA were analysed using phylogenetic techniques to identify whether landmasses are monophyletic and what the relationships are between landmasses. Molecular clock dating methods were used to date divergences between taxa. Results Each landmass was recovered as monophyletic. Japan/Ryukyu Islands is the most basal group, followed by New Zealand. Australian specimens form a sister group to a clade made up of two groups (New Caledonia and Lord Howe/Norfolk Island). The oldest divergence within the genus (between North and South Pacific) took place 12–19 Ma. Main conclusions The geographical origin of the genus (either Gondwana or Laurasia) is unclear. Dispersal occurred between the North and South Pacific long after the split up of Gondwana. Dispersal likely explains the presence of Paratya on each landmass in the South Pacific, from continent to isolated oceanic island. This dispersal is conjectured to have taken place through oceanic currents because of the amphidromous life cycle of some taxa of Paratya, given that amphyidromy is plesiomorphic in atyid shrimp.     

Geometric morphometrics of carapace of Macrobrachium australe (Crustacea: Palaemonidae) from Reunion Island

Zimmermann, G., Bosc, P., Valade, P., Cornette, R., Améziane, N. and Debat, V. 2011. Geometric morphometrics of carapace of Macrobrachium australe (Crustacea: Palaemonidae) from Reunion Island. —Acta Zoologica (Stockholm) 93 : 492–500. We investigated the structure of carapace shape variation in six populations of Macrobrachium australe Guérin‐Méneville 1838 (Crustacea: Decapoda: Palaemonidae) from Reunion Island (Indian Ocean) freshwaters. The morphometric analysis revealed the occurrence of two morphotypes corresponding to two different types of habitats. Individuals living in lotic habitats present a thick carapace armed with a short, robust and straight rostrum, while individuals from lentic habitats have a slender carapace armed with a thin long rostrum orientated upward. This difference suggests an adaptation to lotic disturbances and is tentatively interpreted as adaptive phenotypic plasticity. In such amphidromous organisms regressing to freshwaters after a marine larval phase, selection for physiological and developmental flexibility might facilitate further adaptation and allows the colonisation of a wide panel of environmentally different and sometimes geographically distant insular streams.     

Reproductive biology of the endemic goby, Lentipes concolor, from Makamaka'ole Stream, Maui and Waikolu Stream, Moloka'i

Constant pressure in Hawai'i to use limited freshwater resources has resulted in increasing concern for the future of the native stream fauna. Hawaiian freshwater gobies have an amphidromous life cycle with a marine larva period and require streams which flow continuously to the ocean for the critical reproductive periods and during recruitment. As such, the stream fauna is particularly sensitive to any anthropogenic perturbations which disrupt the continuity of stream flows. The objective of this 2-year study was to compare the life cycles of the goby, Lentipes concolor, from a heavily diverted stream on Moloka'i and a relatively undisturbed stream on Maui. In Makamaka'ole Stream, Maui, the population of L. concolor was reproductively active all year with females potentially spawning 2–3 times annually. The timing of spawning did not occur consistently during the wet or dry season but coincided with high stream flow conditions regardless of time-of-year. In Waikolu Stream, Moloka'i, the reproductive pattern was more variable with the number of reproductively active females ranging from 0% to 100%. In general the number of eggs was greater and egg size smaller for female L. concolor in Waikolu Stream than in Makamaka'ole Stream. However, female reproductive condition of L. concolor from Maui was consistently higher than from fish on Moloka'i. Reproduction of L. concolor in Makamaka'ole Stream was correlated with the seasonal pattern of flow rates with peaks in female reproductive condition associated with periods of elevated discharge. No correlation between reproduction and discharge occurred in Waikolu Stream. There were considerable differences between the magnitude of discharge in the two streams. Waikolu Stream experienced prolonged periods of extremely low flows which have become common since the Moloka'i Irrigation System began diverting water from the stream in 1960. In Makamaka'ole Stream, L. concolor was capable of reproducing throughout the year and adjusting fecundity in response to stream flow conditions. In contrast, the population in Waikolu Stream appeared to have a ‘boom or bust’ reproductive pattern; the population had reduced or no reproduction when stream flow conditions reached extreme low levels, but the population succesfully reproduced during higher flow months. The diversion structure in Waikolu Stream has dampened the natural seasonal discharge cycle, exacerbated natural low flow conditions, and increased the likelihood of prolonged periods of extremely low flow. Stream management practices in the Hawaiian Islands must take into account the complex life cycles and sensitivity to variable stream flow conditions of the native fauna. This revised version was published online in July 2006 with corrections to the Cover Date.     

Overcoming urban stream syndrome: Trophic flexibility confers resilience in a Hawaiian stream fish

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Genetic population structure in prickly sculpin (Cottus asper) reflects isolation‐by‐environment between two life‐history ecotypes

Life‐history transitions have evolved repeatedly in numerous taxa, although the ecological and evolutionary conditions favouring such transitions in the presence of gene flow remain poorly understood. The present study aimed to disentangle the effects of isolation‐by‐distance and isolation‐by‐environment on genetic differentiation between two sympatric life‐history ecotypes. Using 14 microsatellite loci, we first characterized amphidromous and freshwater groups of Cottus asper in a high gene flow setting in the Lower Fraser River system (south‐western British Columbia, Canada) to test for the effects of habitat and geographical distance on the distribution of life‐history ecotypes. Within the main river channel, no genetic differentiation was found, whereas tributaries even close to the estuary were genetically differentiated. Partial mantel tests confirmed that genetic differentiation between river tributaries and the main channel was independent from geographical distance, with distance‐scaled migration rates indicating reduced gene flow from the main channel into the tributaries. Our results suggest that isolation‐by‐environment can play an important role for the early stage of life‐history transitions, and may promote differentiation among life‐history ecotypes despite the presence of gene flow. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 943–957.     

Yellow-stage American eel movements determined by microtagging and acoustic telemetry in the St Jean River watershed, Gaspé, Quebec, Canada

The hypothesis that a part of the yellow American eel Anguilla rostrata sub-population of the St Jean River in eastern Quebec feeds in the brackish environment during summer and returns to the river to overwinter was tested. Three years of microtagging and the acoustic tagging and tracking of 40 American eels demonstrated that a part of the downstream migrants exploited the estuary as a summer feeding area. Upstream movement of some microtagged American eels provided support for the hypothesis that a part of those American eels returned to the river to overwinter. In addition to the demonstration of amphidromous behaviour of yellow eels, the study revealed that American eels in the estuary were active at night but homed to specific daytime resting sites.     

Molecular evidence for sequential colonization and taxon cycling in freshwater decapod shrimps on a Caribbean island

Taxon cycling, i.e. sequential phases of expansions and contractions in species' distributions associated with ecological or morphological shifts, are postulated to characterize dynamic biogeographic histories in various island faunas. The Caribbean freshwater shrimp assemblage is mostly widespread and sympatric throughout the region, although one species (Atyidae: Atya lanipes) is geographically restricted and ecologically and morphologically differentiated from other Atya species. Using patterns of nucleotide variation at the COI mtDNA gene in five species of freshwater shrimp (A. lanipes, A. scabra, A. innocuous; Xiphocarididae: Xiphocaris elongata; Palaemonidae: Macrobrachium faustinum) from Puerto Rico, we expected to detect a signature of sequential colonization in these shrimp, consistent with the concept of taxon cycling, and expected that A. lanipes would be at a different taxon stage (i.e. an early stage species) to all other species. We also examined patterns of genetic population structure in each species expected with poor, intermediate and well-developed abilities for among-river dispersal. Population expansions were detected in all species, although the relative timing of the expansions varied among them. Assuming that population expansions followed colonization of Puerto Rico by freshwater shrimp, results bear the hallmarks of sequential colonization and taxon cycling in this fauna. A. lanipes had a star phylogeny, low mean pairwise nucleotide differences and recent (Holocene) estimates for an in situ population expansion in Puerto Rico, and it was inferred as an early stage species in the taxon cycle undergoing a secondary phase of expansion. All other species were inferred as late stage species undergoing regional population expansions, as their mean pairwise nucleotide differences were relatively high and phylogenetic patterns were more complex than A. lanipes. High rates of gene flow without isolation by distance among rivers were detected in all species, although results should be treated cautiously as some populations are unlikely to be in mutation-drift equilibrium. Nested clade analysis produced inconsistent results among species that all have high rates of gene flow and expanding populations.     

Diverse migratory histories in a brackish water type of the ninespine stickleback, <Emphasis Type="Italic">Pungitius pungitius</Emphasis>

The life history in a brackish water type of the ninespine stickleback, Pungitius pungitius, was studied by examining the strontium (Sr) and calcium (Ca) concentrations in the otoliths. The fluctuating patterns of Sr/Ca ratios along the life history transect in the otoliths varied widely among fish in spite of their identification as brackish water type as estimated by morphological characteristics. More than 70% fish showed the intermediate otolith Sr/Ca ratio throughout, averaging 5.23–7.71 × 10⁻³. Besides this brackish water resident life history type of P. pungitius, other sticklebacks had anadromous (25%) and freshwater amphidromous (2.5%) life history types. These findings clearly indicate that the migration of the ninespine stickleback between fresh and sea waters is obligatory but facultative having an ability to utilize the full range of salinity in its life history.