Christmas Island

• Like the heat waves on land we have all grown familiar with, marine heat waves are being amplified by climate change.
• These extreme warm water events have ushered in some of the most catastrophic impacts of climate change and are now a major threat to ocean life.
• As climate change pushes corals beyond their limits, a key question is why different corals vary in their sensitivity to warm waters.

Pushing corals out of their comfort zones

• Corals are highly adapted to the temperature of their local waters, with temperatures even 1 C warmer than normal pushing them out of their comfort zone.
• Unusually warm water disrupts the vital relationship between stony corals (the reef-builders) and their symbiotic partners, microscopic algae that provide food to the corals.

Cryptic diversity within a widespread coral species

• We focused on the widespread lobed coral (Porites lobata).
• This species is amongst the most heat-tolerant corals, and despite almost 90 per cent of all coral cover being lost on Kiritimati, over half of lobed corals survived.
• Such biodiversity is known as “cryptic diversity” or “hidden diversity.” Although cryptic diversity is widespread across corals, its ecological implications remain unclear.

Marine heat waves threaten cryptic diversity

• Thus, even in a coral widely considered to be stress tolerant, heat waves can have hidden impacts, threatening diversity that is invisible to the naked eye.
• Hardly – the Barrier Reef is still in hot water

  If future marine heat waves continue to have similar effects, eventually sensitive genotypes like this one could be completely lost, reducing the genetic diversity of coral reefs.

A forced breakup

• One hypothesis is that they house symbiotic partners with different heat sensitivities.
• We found that the distinct Porites lineages had different partnerships before the heat wave.
• The survivors of all lineages had similar symbionts, suggesting specialized relationships between the partners had been lost under extreme temperatures.

Implications for conserving coral reefs

• Cryptic species often occupy unique ecological niches and play specific roles within ecosystems.
• Using heat tolerant cryptic lineages in restoration approaches, for example, could help make reefs more tolerant to future warming.
• While targeted efforts to bolster coral reefs against climate change may buy limited time, the current heat waves blanketing the world’s oceans underscore that the ocean is simply becoming too hot for corals and we need to act rapidly to mitigate the damage.

• Red imported fire ants have been detected for the first time on the western side of the Great Dividing Range in Toowoomba, Queensland.
• The yellow crazy ant (Anoplolepis gracilipes) ranks among the world’s 100 worst animal pests because of its impacts on agriculture and biodiversity.
• The red imported fire ant (Solenopsis invicta) poses similar threats, and is also one of the world’s most dangerous ants.

Read more:
Eradicating fire ants is still possible, but we have to choose now

Where did the crazy ants come from?

• The origin of yellow crazy ants is disputed but is likely in South-East Asia or Africa.
• It can burn human skin and is lethal for other ants and many native arthropods.
• These ants have spread to much of South-East Asia, parts of central America and the United States.
• Since reaching the Australian territory of Christmas Island, yellow crazy ants have devastated the native wildlife.
• The prospects of total eradication of yellow crazy ants in Australia are not promising.

And what about the fire ants?

• The fire ants are less distinctive than the crazy ants.
• They look like some small native ants in the genera Monomorium and Chelaner.
• However, their antennae have two segments, while these native ants have three segments.
• They are distinguished by the teeth on the mandible, or jaws: the red imported fire ant has four teeth and the other species has three.
• It has super-colonies like the crazy ant and is equally adaptable in terms of food, nest sites and multiple queens (in some, but not all colonies).