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River corridor plants in Central Europe account for an above-average proportion of endangered species. The main objective of this study was to examine the effects of habitat fragmentation and abiotic conditions on the survival and changes in population size of four endangered, long-lived river corridor plant species (Euphorbia palustris, Pseudolysimachion longifolium, Sanguisorba officinalis, and Senecio paludosus) over the course of at least ten years. We sampled altogether 138 populations in the Weser and Elbe river systems in Northwestern Germany.
Overall, 33% of the populations went extinct during the study period. Extinction rates and changes in population size were related to initial population sizes, but not to population isolation and only marginally so to habitat quality. Large populations (> 100 individuals) had a much higher probability to survive or increase in size (to > 1000 individuals) than smaller populations. There was no general decline in population size in surviving populations, and extinction rates and changes in population size were independent of time. We therefore conclude that the high extinction rates in small populations are best explained by sudden short-term environmental events, such as changes in land use, rather than by long-term negative effects of, for example, genetic deterioration. A projection matrix for the next 117 years, however, predicted that 85% of the surveyed populations will have gone extinct. Since any establishment of new populations in the study area is unlikely owing to the lack of potential habitats and dispersal limitation, river corridor plants will probably continue to decline. Apart from preventing further habitat deterioration it will be crucial to maintain or establish an appropriate management, and to avoid sudden and adverse changes in land use.
Market fragmentation and technological advances increasing the speed of trading altered the functioning and stability of global equity limit order markets. Taking market resiliency as an indicator of market quality, we investigate how resilient are trading venues in a high-frequency environment with cross-venue fragmented order flow. Employing a Hawkes process methodology on high-frequency data for FTSE 100 stocks on LSE, a traditional exchange, and on Chi-X, an alternative venue, we find that when liquidity becomes scarce Chi-X is a less resilient venue than LSE with variations existing across stocks and time. In comparison with LSE, Chi-X has more, longer, and severer liquidity shocks. Whereas the vast majority of liquidity droughts on both venues disappear within less than one minute, the recovery is not lasting, as liquidity shocks spiral over the time dimension. Over half of the shocks on both venues are caused by spiralling. Liquidity shocks tend to spiral more on Chi-X than on LSE for large stocks suggesting that the liquidity supply on Chi-X is thinner than on LSE. Finally, a significant amount of liquidity shocks spill over cross-venue providing supporting evidence for the competition for order flow between LSE and Chi-X.