Integrated Population Genomic Analysis and Numerical Simulation to Estimate Larval Dispersal of Acanthaster cf. solaris Between Ogasawara and Other Japanese Regions

The estimation of larval dispersal on an ecological timescale is significant for conservation of marine species. In 2018, a semi-population outbreak of crown-of-thorns sea star, Acanthaster cf. solaris, was observed on a relatively isolated oceanic island, Ogasawara. The aim of this study was to assess whether this population outbreak was caused by large-scale larval recruitment (termed secondary outbreak) from the Kuroshio region. We estimated larval dispersal of the coral predator A. cf. solaris between the Kuroshio and Ogasawara regions using both population genomic analysis and simulation of oceanographic dispersal. Population genomic analysis revealed overall genetically homogenized patterns among Ogasawara and other Japanese populations, suggesting that the origin of the populations in the two regions is the same. In contrast, a simulation of 26-year oceanographic dispersal indicated that larvae are mostly self-seeded in Ogasawara populations and have difficulty reaching Ogasawara from the Kuroshio region within one generation. However, a connectivity matrix produced by the larval dispersal simulation assuming a Markov chain indicated gradual larval dispersal migration from the Kuroshio region to Ogasawara in a stepping-stone manner over multiple years. These results suggest that the 2018 outbreak was likely the result of self-seeding, including possible inbreeding (as evidenced by clonemate analysis), as large-scale larval dispersal from the Kurishio population to the Ogasawara population within one generation is unlikely. Instead, the population in Ogasawara is basically sustained by self-seedings, and the outbreak in 2018 was also most likely caused by successful self-seedings including possible inbreeding, as evidenced by clonemate analysis. This study also highlighted the importance of using both genomic and oceanographic methods to estimate larval dispersal, which provides significant insight into larval dispersal that occurs on ecological and evolutionary timescales.

BIOLOGICAL INVASIONS: THE EUROPEAN SMELT OSMERUS EPERLANUS (L.) AND THE MICROSPORIDIAN GLUGEA HERTWIGI WEISSENBERG, 1911

The paper presents the phenomenology of the smelt Osmerus eperlanus and the microsporidian Glugea hertwigi invasion into a new habitat - Lake Syamozero (Karelia), where neither of the species occurred before. The invasion history falls into 4 phases. The first, latent phase started with a spontaneous invasion of the lake by smelt and lasted until the first fish showed up in catches (1968-1970). The second phase (1971 to 1980) was the invader number outbreak. The smelt became the dominant species in the fish community, while the native plankton-feeder, the vendace Coregonus albula, became an endangered species. The third phase (1980 to 1991) was the population outbreak of the microsporidian Glugea hertwigi, and development of an epizootic. The fourth phase (since 1991 until present) is the decreasing of the number of the invasive species - the smelt and the microsporidian Glugea hertwigi and the recovery of the native vendace population.

First report of damage and population dynamics of Raoiella indica Hirst (Acari: Tenuipalpidae) on Euterpe oleracea (Arecaceae) in the State of Bahia, Brazil

The presence of the red palm mite Raoiella indica Hirst, was recorded on açaí, Euterpe oleracea Mart. (Arecaceae), in Porto Seguro, Bahia State, northeastern Brazil. We evaluated the population dynamics of R. indica from September 2019 to February 2020. The population outbreak and most severe damage caused by R. indica was observed in February, a period of highest temperatures and low relative humidity. This is the first report of damage caused by the red palm mite on E. oleracea in Brazil. Management practices must be implemented to avoid intercropping açaí with other hosts of this mite e.g. coconut, banana and palm trees in order to minimize the occurrence and damage of R. indica on such agrosystems.

Integrated population genomic analysis and numerical simulation to estimate larval dispersal of Acanthaster cf. solaris between Ogasawara and other Japanese regions

The estimation of larval dispersal of marine species occurring on an ecological timescale is significant for conservation. In 2018, a semi-population outbreak of crown of thorns starfish, Acanthaster cf. solaris was observed on a relatively isolated oceanic island, Ogasawara. The aim of this study was to assess whether this population outbreak was caused by large-scale larval recruitment (termed secondary outbreak) from the Kuroshio region. We estimated larval dispersal of the coral predator A. cf. solaris between the Kuroshio and Ogasawara regions using both population genomic analysis and oceanographic dispersal simulation. Population genomic analysis revealed overall genetically homogenized patterns among Ogasawara and other Japanese populations, suggesting that the origin of the populations in the two regions is the same. In contrast, a simulation of 26-year oceanographic dispersal indicated that larvae are mostly self-seeded in Ogasawara populations and have difficulty reaching Ogasawara from the Kuroshio region within one generation. However, a connectivity matrix produced by the larval dispersal simulation assuming a Markov chain indicated gradual larval dispersal migration from the Kuroshio region to Ogasawara in a stepping-stone manner over multiple years. These results suggest that, while large-scale larval dispersal from an outbreak of the Kuroshio population spreading to the Ogasawara population within one generation is unlikely. This study also highlighted the importance of using both genomic and oceanographic methods to estimate larval dispersal, which provides significant insight into larval dispersal that occurs on ecological and evolutionary timescales.

fractal biology of plague and the future of civilization

At the time of writing, the CoViD-19 pandemic was in its second wave with infections doubling every several days to two weeks in many parts of the world. Such geometric (or exponential) expansion is the hallmark of unconstrained population growth in all species ranging from submicroscopic viral particles through bacteria to whales and humans; this suggests a kind of ‘fractal geometry’ in bio-reproductive patterns. In nature, population outbreaks are invariably reversed by the onset of both endogenous and exogenous negative feedback – reduced fecundity, resource shortages, spatial competition, disease, etc., serve to restore the reference population to below carrying capacity, sometimes by dramatic collapse. H. sapiens is no exception – our species is nearing the peak of a fossil-fueled ~200 year plague-like population outbreak that is beginning to trigger serious manifestations of negative feedback, including climate change and CoViD-19 itself. The human population will decline dramatically; theoretically, we can choose between a chaotic collapse imposed by nature or international cooperation to plan a managed, equitable contraction of the human enterprise.

Homing behaviour by destructive crown-of-thorns starfish is triggered by local availability of coral prey

Corallivorous crown-of-thorns starfishes ( Acanthaster spp.) can decimate coral assemblages on Indo-Pacific coral reefs during population outbreaks. While initial drivers of population irruptions leading to outbreaks remain largely unknown, subsequent dispersal of outbreaks appears coincident with depletion of coral prey. Here, we used in situ time-lapse photography to characterize movement of the Pacific crown-of-thorns starfish ( Acanthaster cf. solaris ) in the northern and southern Great Barrier Reef in 2015, during the fourth recorded population outbreak of the starfish, but prior to widespread coral bleaching. Daily tracking of 58 individuals over a total of 1117 h revealed all starfish to move a minimum of 0.52 m, with around half of all tracked starfish showing negligible daily displacement (less than 1 m day −1 ), ranging up to a maximum of 19 m day −1 . Movement was primarily nocturnal and daily displacement varied spatially with variation in local availability of Acropora spp., which is the preferred coral prey. Two distinct behavioural modes emerged: (i) homing movement, whereby tracked paths (as tested against a random-walk-model) involved short displacement distances following distinct ‘outward' movement to Acropora prey (typically displaying ‘feeding scars') and ‘homebound' movement to nearby shelter; versus (ii) roaming movement, whereby individuals showed directional movement beyond initial tracking positions without return. Logistic modelling revealed more than half of all tracked starfish demonstrated homing when local abundance (percentage cover) of preferred Acropora coral prey was greater than 33%. Our results reveal facultative homing by Acanthaster with the prey-dependent behavioural switch to roaming forays providing a mechanism explaining localized aggregations and diffusion of these population irruptions as prey is locally depleted.