Geschlechterwandel durch Klimawandel: Alarmgeschichten von Meeresschildkröten und schrumpfenden grönländischen Schmetterlingen

Die Florida Atlantic University hat Sensationelles herasugefunden: Der Klimawandel verändert die Geschlechterbalance von Meeresschildkröten! Das war eine umfangreiche Pressemitteilung wert, die am 15. Oktober 2015 das Licht der Welt erblickte:

Sex and Sea Turtles: New FAU Study Reveals Impact of Climate Change, Sea Level Rise

Marine turtles deposit their eggs in underground nests where they develop unattended and without parental care. Incubation temperature varies with environmental conditions, including rainfall, sun, shade and sand type, and affects developmental rates, hatch and emergence success, and embryonic sex. Although the loggerhead turtle has been around for more than 60 million years, drought, heavy rainfalls and climatic changes are impacting hatchling sex ratios and influencing future reproduction. Because sea turtles don’t have an X or Y chromosome, their sex is defined during development by the incubation environment. Warmer conditions produce females and cooler conditions produce males.

Researchers from Florida Atlantic University have just published the results of a four-year study in the journal Endangered Species Research, on the effects of turtle nest temperatures and sand temperatures and on hatchling sex. “The shift in our climate is shifting turtles as well, because as the temperature of their nests change so do their reproduction patterns,” said Jeanette Wyneken, Ph.D., professor of biological sciences in FAU’s Charles E. Schmidt College of Science. “The nesting beaches along Florida’s coast are important, because they produce the majority of the loggerhead hatchlings entering the northwestern Atlantic Ocean.”

Loggerhead turtles are already fighting an uphill battle since roughly one in 2,500 to 7,000 sea turtles make it to adulthood. The typical loggerhead produces about 105 eggs per nesting season and would have to nest for more than 10 nesting seasons over the span of 20 to 30 years just to replace herself and possibly one mate. And, if enough males aren’t produced because of climate changes, then this will result in a dire problem for this species. “If climatic changes continue to force the sex ratio bias of loggerheads to even greater extremes, we are going to lose the diversity of sea turtles as well as their overall ability to reproduce effectively. Sex ratios are already strongly female biased,” said Wyneken. “That’s why it’s critical to understand how environmental factors, specifically temperature and rainfall, influence hatchling sex ratios.”

Wyneken and her team documented rainfall and sand temperature relationships as well as rainfall, nest temperatures and hatchling sex ratios at a loggerhead turtle nesting beach in Boca Raton, located in southeast Florida. Nesting season, which runs from April through October, were sampled across 2010 and 2013. The researchers used temperature dataloggers in the sand at three locations and buried them at three different depths to create temperature profiles of the sand column above the level that would directly influence eggs. The rainfall data were graphed in temporal synchrony with sand temperature for each depth. Nest temperatures were recorded throughout incubation. Rainfall data collected concurrently with sand temperatures at different depths showed that light rainfall affected only the surface sand; effects of the heaviest rainfall events tended to lower sand temperatures, however, the temperature fluctuations were very small once the moisture reached upper nest depths.

Nest temperature profiles were synchronized with rainfall data from weather services to identify relationships with hatchling sex ratios. The sex of each turtle was verified laparoscopically to provide empirical measures of sex ratios for the nest and the nesting beach. “The majority of hatchlings in the sampling were female, suggesting that across the four seasons most nest temperatures were not sufficiently cool to produce males,” said Wyneken. “However, in the early portion of the nesting and in wet years, nest temperatures were cooler, and significantly more males hatched.”

Als ob die Schildkröten-Geschichte noch nicht schlimm genug war, legte die dänische Universität Aarhus ein paar Tage später noch nach. Diesmal schrumpft der Klimawandel grönländische Schmetterlinge, was hochbedauerlich und relevant ist. Hier die Presseitteilung:

High-arctic butterflies shrink with rising temperatures

New research shows that butterflies in Greenland have become smaller in response to increasing temperatures due to climate change.

It has often been demonstrated that the ongoing rapid climate change in the Arctic region is causing substantial change to Arctic ecosystems. Now Danish researchers demonstrate that a warmer Greenland could be bad for its butterflies, becoming smaller under warmer summers. Researchers from Aarhus University have measured wing length of nearly 4,500 individuals collected annually between 1996 and 2013 from Zackenberg Research Station in Northeast Greenland, and found that wing length has decreased significantly in response to warmer summers and at the same rate for both species investigated. “Our studies show that males and females follow the same pattern and it is similar in two different species, which suggests that climate plays an important role in determining the body size of butterflies in Northeast Greenland,” says senior scientist Toke T. Høye, Aarhus Institute of Advanced Studies, Aarhus University.

Only very few field studies have been able to follow changes in the body size of the same species over a period where the climate has changed and this is the longest known time series on body size variation in butterflies, of which we are aware.

The larvae change metabolism

Body size change in response to rising temperature is an anticipated response to climate change, but few studies have actually demonstrated it in the field. The response can go both ways; for some animal species, a longer feeding season results in increased body size, and for others the changes in metabolism causes a net loss of energy which reduces the body size. The results of the new study are consistent with earlier lab experiments and broad spatial scale studies suggesting that higher temperatures during rearing result in smaller adult body size.

“We humans use more energy when it is cold, because we must maintain a constant body temperature. But for butterfly larvae and other cold-blooded animals whose body temperature depends on the environment, the metabolism increases at higher temperatures because the biochemical processes are simply faster. Therefore, the larvae use more energy than they are able to gain from feeding. Our results indicate that this change is so significant that larval growth rate decreases. And when the larvae are smaller, the adult butterflies will also be smaller,” explains Toke T. Høye.

Arctic species under pressure

The consequences for the Arctic butterflies can be quite substantial. Smaller body size means that the butterflies are less mobile. As the species only live in the far North, the development could have significant consequences for their population dynamics and future geographic range. “These butterfly species are under pressure from multiple sides. They live so far North that they cannot move to cooler regions, and they will probably disappear from the southernmost part of their range due to the warming temperatures. In addition, their dispersal capacity is deteriorating, and smaller body size may result in lower fecundity, so these Arctic species could face severe challenges in response to ongoing rapid climate change,“ says Toke T. Høye.

Butterflies belong to a group of organisms that are particularly sensitive to changes in the environment. Therefore, long-term studies of butterflies and other insects are particularly suited to demonstrate the ecological consequences of global climate change. The study was carried out by researchers at the Arctic Research Centre, Department of Bioscience, and the Aarhus Institute of Advanced Studies, Aarhus University, as well as the Natural History Museum Aarhus and the University of California.

The results have been published in the scientific journal Biology Letters.


Wo wir gerade über die Tierwelt sprechen. berichtete am 16. Oktober 2015 über eine Tierdemo gegen den Klimawandel:

Tierdemo gegen den Klimawandel in Freiburg
Theaterleute hatten für den Freitagnachmittag zu einer Perfomancedemo aufgerufen. 300 kamen – vom Hirsch bis zur Maus: Klima ist blöd, sagt Jella Baur. Die Elfjährige tanzt witzig watschelig mit Pinguinmaske und mit 70 anderen Pinguinwesen vor dem Stadttheater und organisiert blitzschnell, dass ein Dutzend von ihnen wieder und wieder skandieren: „Hilfe, unser Eis schmilzt!“

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