From so simple a beginning

Evolution and Biodiversity

Category: territory

Fruit abundance

10 October 2024 /

White-bearded manakin with rich territory is more successful

White-bearded manakin with rich territorium spends much time to display

A territory with plenty of food is a valuable asset for a male white-bearded manakin. The easier he finds food, the more time he spends on courtship display and the more females will visit him, as Luke Anderson and colleagues show.

In the white-bearded manakin, Manacus manacus, males contribute nothing to the care of the offspring. They occupy a territory in the vicinity of two to dozens of other males and try to attract as many females as possible and seduce them to mate. Females do the rest: after they have selected a male and copulated, they build a nest without help, incubate the eggs and raise the young.

Males with a territory that is rich in the fruits that they eat receive more female visits than males in a place with less food, Luke Anderson and colleagues discovered.

Costly courtship display

The white-bearded manakin, a small songbird, lives in forests in tropical South America. Like in many of the other 55 manakin species, the black-and-white males display spectacular courtship behaviour to attract females during the breeding season. Some males are much more successful than others.

A male possesses a territory in which he has cleared a court – a piece of ground of 15 to 90 centimetres in diameter, surrounded by saplings – down to the bare soil. Clean ground is safe, because a dangerous snake is perceived immediately. Moreover, the male stands out with his show. He puffs out his beard feathers, utters his call and leaps up and down between stems and the ground at lightning speed, his wings snapping and whirring. He can sustain this energetically costly show for up to half a minute at a time.

The olive-green females do best to choose a male of good genetic quality, to maximize the chance to produce successful offspring. An important criterium by which females can judge the quality of males is their courtship performance. The more intense the courtship is, the stronger and healthier the performer will be.

Uneven playing field

But now, Anderson writes that some white-bearded manakin males have an advantage by possessing a rich territory. The birds eat mainly ripe fruits, and territories differ greatly in fruit availability, his research in Ecuador shows. Males with a rich territory have to spend hardly time looking for food and are in good condition, he assumed. And indeed, as camera observations showed: the richer a territory was, the more time its owner spent on his shows.

And the more time a male spent displaying, the higher the frequency of female visits, thus the more reproductive success he had.

So, the displaying males are rivals on an uneven playing field; males with a rich territory are at an advantage. Is courtship performance then an honest signal of their quality?

Competition

It would be an dishonest signal if it is a coincidence whether a white-bearded manakin male occupies a rich territory, his quality having nothing to do with it.

But probably, the males have to compete for the best place, and the highest quality male will obtain the richest territory where he can spend much time on courtship display. In this case, the courtship performance is an honest signal for females to assess male quality.

The birds deposit the seeds of the fruits they eat back into their territory. In this way, places with fruiting plants will continue to exist. Males are long-living and can occupy the same territory for up to eleven years.

Willy van Strien

Photo: White-bearded manakin male. Félix Uribe (Wikimedia Commons, Creative Commons CC BY -SA 2.0)

Watch a video of a displaying white-bearded manakin male on You Tube

Sources:
Anderson, H.L., J. Cabo & J. Karubian, 2024. Fruit resources shape sexual selection processes in a lek mating system. Biology Letters 20: 20240284. Doi: 10.1098/rsbl.2024.0284
Cestari, C. & M.A. Pizo, 2014. Court cleaning behavior of the white-bearded manakin (Manacus manacus) and a test of the anti-predation hypothesis. The Wilson Journal of Ornithology, 126: 98-104. Doi: 10.1676/13-032.1

Reinforced carton

18 April 2023 /

Crematogaster clariventris grows a fungus that strengthens its nest wall

Crematogaster clariventris grows a fungus that reinforces its nest

Workers of the ant Crematogaster clariventris collect pieces of fresh leaves to grow a fungus, Alain Dejean and colleagues observed. The threads of the fungus reinforce the carton nest of the ants.

Fungus threads as a component of building or insulation material: you hear more and more about it. It is considered to be innovative, but……. ants were ahead of us. Some species strengthen the walls of their nests with fungal hyphae (threads). The African ant Crematogaster clariventris even collects fresh pieces of leaves to feed them to a fungus that forms strong hyphae, Alain Dejean and colleagues discovered.

The ant lives in large colonies, high in trees. On main branches, workers build nests of hard carton, which they make by chewing fibrous plant material, such as hairs (trichomes) or pieces of wood. They add a fungus, with the result that a network of branched fungal hyphae is embedded in the carton walls; the hyphae consist of tubular cells with a sturdy cell wall. The nest wall is a natural composite material.

Fresh leaf

Dejean, who works in Cameroon, noticed that workers of Crematogaster clariventris bring freshly cut pieces of young and nutritious plant leaves whenever a new nest is constructed or a damaged part of a nest is repaired. Other workers add chewed pulp, and the whole hardens into fungus-reinforced carton in a few days. From these observations, the researchers deduce that the ants bring the fresh leaf material as food for the fungus that forms reinforcing hyphae, so that it will grow well in the new nest wall.

After the fungus died, the sturdy hyphae in the nest wall remain intact.

Crematogaster clariventris is not the only ant species to cut off pieces of leaves to grow a fungus. In Central and South America, ant species occur that cut pieces of fresh leaves and carry it to fungus gardens in their underground nests, the leafcutter ants. They grow fungus for food. So, ants also preceded us in agriculture.

Willy van Strien

Photo: Crematogaster clariventris ©Piotr Naskrecki

Source:
Dejean, A., P. Naskrecki, C. Faucher, F. Azémar, M. Tindo, S. Manzi & H. Gryta, 2023. An Old World leaf-cutting, fungus-growing ant: A case of convergent evolution Ecology & Evolution 13: e9904. Doi: 10.1002/ece3.9904

Gaping display

24 October 2022 /

Sarcastic fringehead impresses with giant upper jaw

sarcastic fringehead can open its mouth extraordinary wide

Males of the blenny Neoclinus blanchardi, the sarcastic fringehead, can open their mouths extraordinary wide. They perform their gaping display for nothing but impressing each other, Watcharapong Hongjamrassilp and colleagues show.

It is an amazing scene when Neoclinus blanchardi fully opens its mouth. A huge membrane becomes visible, consisting of palate and cheeks. It is vividly coloured and has a yellow margin.

In English, the fish is called sarcastic fringehead; it lives along the coast of California. It was already known that males, that have a larger mouth than females, impress each other with it. Now, Watcharapong Hongjamrassilp and colleagues show that they perform their elaborate display for that purpose exclusively.

Wrestling

The sarcastic fringehead can open a large mouth thanks to an upper jaw that is enlarged compared to related fish species and that grows longer than the rest of the body. Its posterior part is unossified and flexible and extends beyond the head. The jaw is connected to the skull in such a way that it can be rotated laterally.

As said, males signal by gaping to scare off each other. A successful male manages to occupy an empty snail shell or a rock crevice in which he hides with only his head protruding. He tries to attract a female. When she likes him, she will lay eggs in his shelter. He fertilizes the eggs and takes care of them until the young hatch. When another male invades his territory, he approaches him, performing the gape display.

The intruder either retreats immediately, or he persists and returns the display. Then the males clash and push each other with the open mouths pressed together. The bigger a male is, the wider his gape. The smallest usually loses, sometimes after the victor had bitten him.

Apparently, suitable shelters are so scarce that the fish has developed a special weapon to defend its place.

Missed opportunity?

But the sarcastic fringehead’s exaggerated gape would also be impressive enough to scare away predators, Hongjamrassilp thought. Or enticing enough to seduce females. He scuba-dove into the water and conducted experiments in the laboratory to see whether this happens.

It did not. If a predator looms, the sarcastic fringehead chases it away by burst swimming. And when a female shows up, he rapidly shakes his head side to side to arouse her interest. He keeps his amazing mouth closed in both cases.

A missed opportunity, you might say.

Willy van Strien

Photo: Neoclinus blanchardi in its shelter. Magnus Kjaergaard (Wikimedia Commons, Creative Commons CC BY-SA 2.5)

This video shows the gaping display

Sources:
Hongjamrassilp, W., Z. Skelton & P.A. Hastings, 2022. Function of an extraordinary display in Sarcastic Fringeheads (Neoclinus blanchardi) with comments on its evolution. Ecology, online Octobre 6: e3878. Doi: 10.1002/ecy.3878
Hongjamrassilp, W., A.P. Summers & P.A. Hastings, 2018. Heterochrony in fringeheads (Neoclinus) and amplification of an extraordinary aggressive display in the Sarcastic Fringehead (Teleostei: Blenniiformes). Journal of Morphology 279: 626-635. Doi:10.1002/jmor.20798

Garden or nameplate?

16 September 2021 /

Why vicuñas create communal dung piles

Vicuñas use permanent latrines to defecate and urinate

Vicuñas live in arid, cold and barren areas, high in the Andes. They set up permanent places to defecate and urinate and use those latrines for decades. There is disagreement about why.

High in the South American Andes, where the soil is arid, rocky, and barren, some places stand out because they are green, overgrown with plants. The greens islands developed because vicuñas come there repeatedly to defecate and urinate. Why do they use such latrines? To create gardens with plants that they can feed on, Kelsey Reider and Steven Schmidt suggest. No, the dung piles are kind of nameplates that mark their territory, William Franklin thinks.

Unpalatable bunch grass

Vicuñas are one of the few animal species that live in the Andes at altitudes of more than 4000 meters, right up to the edge of snow. They mainly live in groups that roam over a territory of almost 20 square kilometers. Climate change is also noticeable here; glaciers dwindle and retreat to the mountain tops. Where they melt, a bare bottom appears which is poor in plant nutrients, so that it takes decades before a noteworthy vegetation is formed. Vicuñas are the first to enter the newly exposed soil at the edge of the glaciers.

With their droppings, they enrich the soil with nutrients. They defecate and urinate only on permanent latrines or dung piles which persist for decades. Consequently, fertilized places are created where vegetation can develop more quickly.

First, a vegetation appears that is dominated by the tough and little nutritious Peruvian feather grass, Stipa pichu. It is not until hundreds of years later that a grassier vegetation develops, with the grass Calamagrostis vicunarum, other grasses and herbs.

Peaceful

In those grassy places vicuñas forage preferentially. Because the places are still used as latrines also, the animals run the risk of picking up gastrointestinal parasites. But places with tasty vegetation are so scarce that it is worth the risk.

That is why Reider and Kelsey believe that the vicuñas maintain latrines in order to concentrate their dung and accelerate the development of nutritious vegetation locally. In other words, latrines are gardens where they grow food.

Franklin thinks otherwise, however. Vicuñas that use a young latrine at the edge of a glacier or start a new one will not be able to enjoy a tasty yield themselves, because generations will have passed before there will grow anything edible. When it comes to food breeding, it would be better for an animal to choose an older latrine where plant growth is already substantial.

Instead, he thinks that the dung piles mark the territory of a group. This is important because if an animal enters another group’s territory accidently, it will be violently attacked and chased away and is at risk of serious injury. By marking the territory at fixed places with the characteristic group scent, especially at the borders, a group manages to keep its members within their own safe territory. So, at a border, two groups may be seen peacefully grazing side by side, each in its own area.

Side-effect

Every group member contributes to these scent markings, and whoever contributes benefits from the fact that the nameplate is maintained.

As a result, vegetation develops on bare ground, gradually becoming more attractive. Which is a nice side-effect for future generations and other mammals that visit the grassy places: mountain viscacha (Lagidium viscacia) and Andean fox (Lycalopex culpaeus).

Willy van Strien

Photo: Dick Culbert (Wikimedia Commons, Creative Commons CC BY 2.0)

Sources:
Franklin, W., 2021. Vicuña dung gardens at the edge of the cryosphere: Comment. Ecology 102: e03522. Doi: 10.1002/ecy.3522
Reider, K.E. & S.K. Schmidt, 2021. Vicuña dung gardens at the edge of the cryosphere. Ecology 102: e03228. Doi: 10.1002/ecy.3228

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