Plants and animals can also live in marriage

When we think about the life of plants it is difficult to imagine without interaction with the animals, as they establish different symbiotic relationships day after day. These symbiotic relationships include all the herbivores, or in the contradictory way, all the carnivorous plants. But there are many other super important interactions between plants and animals, such as the relationships that allow them to help each other and to live together. So, this time I want to present mutualism between plants and animals.

And, what is mutualism? it is the relationship established between two organisms in which both benefit from living together, i.e., the two get a reward when they live with the other. This relationship increase their biological effectiveness (fitness), so there is a tendency to live always together.

According to this definition, both pollination and seed dispersal by animals are cases of mutualism. Let’s see.

POLLINATION BY ANIMALS

Many plants are visited by animals seeking to feed on nectar, pollen or other sugars they produce in their flowers and, during this process, the animals carry pollen from one flower to others, allowing it reaches the stigma in a very effective way. Thus, the plant gets the benefit of fertilization with a lower cost of pollen production, which would be higher if it was dispersed through the air. And the animals, in exchange, obtain food. Therefore, a true relationship of mutualism is stablished between the two organisms.

 “Video:The Beauty of Pollination” – Super Soul Sunday – Oprah Winfrey Network (www.youtube.com)

The extreme mutualism occurs when the species evolve depending on the other organism, i.e., when there is coevolution. We define the coevolution such as these evolutionary adaptations that allow two or more organisms to establish a deep relationship of symbiosis, due that the evolutionary adaptations of one specie influence the evolutionary adaptations of another organism. For example, this occurs between various orchids and their pollinators, as is the well- known case of Darwin’s orchid. But there are many other plants that also have co-evolved with their pollinators, as a fig tree or cassava.

In no way, this should be confused with the trickery produced by some plants to their pollinators, that is, when they do not obtain any direct benefit. For example, some orchids can attract their pollinators through odours (pheromones) and their curious forms that resemble female pollinator, stimulating them to visit their flowers. The pollinators will be impregnated with pollen, which will be transported to other flowers due to the same trickery.

Bee orchid (Ophrys apifera) (Autnor: Bernard DUPONT, flickr).

SEED DISPERSAL BY ANIMALS

The origin of seed dispersal by animals probably had occurred thanks to a co-evolutionary process between animals and mechanisms of seed dispersal in which both plants and animals obtain a profit. The most probably is that this process began in the Carboniferous (~ 300MA), as it is believed that some plants like cycads developed a false fleshy fruits that could be consumed by primitive reptiles that would act as seed dispersers. This process could have intensified the diversification of flowering plants (angiosperms), small mammals and birds during the Cretaceous (65-12MA).

The mutualism can occur in two ways within the seed dispersal by animals.

The first case is carried out by animals that eat seeds or fruits. These seeds or some parts of the fruits (diaspores) are expelled without being damaged, by defecation or regurgitation, allowing the seed germination. In this case, diaspores are carriers of rewards or lures that result very attractive to animals. That is the reason why fruits are usually fleshy, sweet and often have bright colours or emit scents to attract them.

For example, the red-eyed wattle (Acacia cyclops) produces seeds with elaiosomes (a very nutritive substance usually made of lipids) that are bigger than the own seed. This suppose an elevated energy cost to the plant, because it doesn’t only have to produce seeds, as it has to generate the award too. But in return, the rose-breasted or galah cockatoo (Eolophus roseicapillus) transports their seeds in long distances. Because when the galah cockatoo eats elaiosomes, it also ingest seeds which will be transported by its flight until they are expelled elsewhere.

On the left,  Galah  cockatoo (Eolophus roseicapillus) (Autnor: Richard Fisher, flickr) ; On the right, red-eyed wattle’s seeds (black) with the elaiosome (pink) ( Acacia cyclops) (Autnor: Sydney Oats, flickr).

And the other type of seed dispersal by animals that establishes a mutualistic relationship occurs when the seeds or fruits are collected by the animal in times of abundance and then are buried as a food storage to be used when needed. As long as not all seed will be eaten, some will be able to germinate.

A squirrel that is recollecting som nuts (Author: William Murphy, flickr)

But this has not finished yet, since there are other curious and less well-known examples that have somehow made that both animals and plants can live together in a perfect “marriage.” Let’s see examples:

Azteca and Cecropia

Plants of the genus Cecropia live in tropical rain forests of Central and South America and they are very big fighters. The strategy that allow them to grow quickly and capture sunlight, avoiding competition with other plants, resides in the strong relationship they have with Azteca ants. Plants provide nests to the ants, since their stems are normally hollow and with separations, allowing ants to inhabit inside. Furthermore, these plants also produce Müllerian bodies, which are small but very nutritive substances rich in glycogen that ants can eat. In return, the ants protect Cecropia from vines and lianas, allowing them to success as a pioneer plants.

Ant Plants: Cecropia – Azteca Symbiosis (www.youtube.com)

Marcgravia and Bats

Few years ago, an interesting plant has been discovered in Cuba. This plant is pollinated by bats, and it has evolved giving rise to modified leaves that act as satellite dish for echolocation performed by these animals. That is, their shape allow bats to locate them quickly, so they can collect nectar more efficiently. And at the same time, bats also pollinate plants more efficiently, as these animals move very quickly each night to visit hundreds of flowers to feed.

Marcgravia (Author: Alex Popovkin, Bahia, Brazil, Flickr)

In general, we see that the life of plants depends largely on the life of animals, since they are connected in one way or another. All the interactions we have presented are part of an even larger set that make life a more complex and peculiar one, in which one’s life cannot be explained without the other’s life. For this reason, we can say that life of some animals and some plants resembles a marriage.

REFERENCES

• Notes from the Environmental Biology degree (Universitat Autònoma de Barcelona) and the Master’s degree in Biodiversity (Universitat de Barcelona).
• Bascompte, J. & Jordano, P. (2013) Mutualistic Networks (Chapter 1. Biodiversity and Plant-Animal Coevolution). Princeton University Press, pp 224.
• Dansereau, P. (1957): Biogeography: an Ecological Perspective. The Ronald Press, New York., pp. 394.
• Fenner M. & Thompson K. (2005). The Ecology of seeds. Cambridge: Cambridge University Press, 2005. pp. 250.
• Font Quer, P. (1953): Diccionario de Botánica. Editorial Labor, Barcelona.
• Izco, J., Barreno, E., Brugués, M., Costa, M., Devesa, J. A., Fernández, F., Gallardo, T., Llimona, X., Parada, C., Talavera, S. & Valdés, B. (2004) Botánica ªEdición. McGraw-Hill, pp. 906.
• Murray D. R. (2012). Seed dispersal. Academy Press. 322 pp.
• Tiffney B. (2004). Vertebrate dispersal of seed plants through time. Annual Review of Ecology, Evolution and Systematics. 35:1-29.
• Willis, K.J. & McElwain, J.C. (2014) The Evolution of Plants (second edition). Oxford University Press, pp. 424.
• National Geographic (2011). Bats Drawn to Plant via “Echo Beacon”. http://news.nationalgeographic.com/news/2011/07/110728-plants-bats-sonar-pollination-animals-environment/

Evolution for beginners 2: coevolution

After the success of Evolution for beginners, today we’ll continue  knowing the basics of biological evolution. Why  exist insects that seem orchids and vice versa? Why gazelles and cheetahs are almost equally fast? Why your dog understands you? In other words, what is coevolution?

WHAT IS COEVOLUTION?

We know that it is inevitable that living beings establish symbiotic relationships between them. Some depend on others to survive, and at the same time, on elements of their environtment as water, light or air. These mutual pressures between species make that evolve together, and as one evolve as a species, in turn it forces the other to evolve. Let’s see some examples:

POLLINATION

The most known process of coevolution is pollination. It was actually the first co-evolutionary study (1859) by Darwin, although he didn’t use that term. The first to use the word coevolution were Ehrlich and Raven (1964).

Insects existed long before the appearance of flowering plants, but their success was due to the discovery that nectar is a good reserve of energy. In turn, the plants found in the insects another way more effectively to carry pollen to another flower. Pollination by the wind (anemophily) requires more production of pollen and a good dose of luck to at least fertilize some flowers of the same species. Many plants have developed flowers that trap insects until they are covered with pollen and then set them free. These insects have hairs in their body to enable this process. In turn some animals have developed long appendages (beaks of hummingbirds, butterflies’ proboscis…) to access the nectar.

Darwin’s moth (Xantophan morganii praedicta). Photo by Minden Pictures/Superstock

It is the famous case of the Darwin’s moth (Xanthopan morganii praedicta) of which we have already talked about. Charles Darwin, studying orchid Christmas (Angraecum sesquipedale) saw that the nectar was 29 cm inside the flower. He sensed that there should exist an animal with a proboscis of this size. Eleven years later, Alfred Russell Wallace reported him that the Morgan’s sphinxs had proboscis over 20 cm long, and a time later they were found in the same area where Darwin had studied that species of orchid (Madagascar). In honor of both it was added “praedicta” to the scientific name.

There are also bee orchids that mimic female insects to ensure their pollination. To learn more about these orchids and the Christmas one, do not miss this post by Adriel.

The bat Anoura fistulata and its long tongue. Photo by Nathan Muchhala

But many plants not only depend on insects, also some birds (like humming birds) and mammals (such as bats) are essential to pollination. The record for the longest mammal tongue in the world is for a bat from Ecuador (Anoura fistulata); its tongue measures 8 cm (150% of the length of its body). It is the only who pollinates one plant called Centropogon nigricans, despite the existence of other species of bats in the same habitat of the plant. This raises the question of whether evolution is well defined, and occurs between pairs of species or it is diffuse due to the interaction of multiple species.

PREDATOR-PREY RELATIONSHIPS

The cheetah (Acinonyx jubatus) is the fastest vertebrate on land (up to 115 km/h). Thomson’s gazelle (Eudorcas thomsonii), the second (up to 80 km/h). Cheetahs have to be fast enough to catch a gazelle (but not all, at risk of disappearing themselves) and gazelles fast enough to escape almost once and reproduce. The fastest gaelles survive, so nature selects in turn faster cheetahs, which are who eat to survive. The pressure from predators is an important factor that determines the survival of a population and what strategies should follow the population to survive. Also, the predators will find solutions to possible new ways of life of their prey to succeed.

Cheetah hunting a Thomson’s gazelle in Kenya. Photo by Federico Veronesi

The same applies to other predator-prey relationships, parasite-host relationships, plants-herbivores, improving their speed or other survival strategies like poison, spikes…

HUMAN AND DOGS … AND BACTERIA

Our relationship with dogs since prehistoric times, it is also a case of coevolution. This allows, for example, to create bonds with just looking at them. If you want more information, we invite you to read this post where we talk about the issue of the evolution of dogs and humans in depth.

Another example is the relationship we have established with the bacteria in our digestive system, essential for our survival. Or with pathogens: they have co-evolved with our antibiotics, so using them indiscriminately has favored these species of bacteria to develop resistance to antibiotics.

THE IMPORTANCE OF COEVOLUTION

Coevolution is one of the main processes responsible for the great biodiversity of the Earth. According to Thompson, is responsible for the millions of species that exist instead of thousands.

The interactions that have been developed with coevolution are important for the conservation of species. In cases where evolution has been very close between two species, if one become extint will lead to the extinction of the other almost certainly. Humans constantly alter ecosystems and therefore biodiversity and evolution of species. Just declining one species, we are affecting many more. This is the case of the sea otter (Enhydra lutris), which feeds on sea urchins.

Sea otter (Enhydra lutris) eating sea urchins. Photo by Vancouver Aquarium

Being hunted for their fur, urchins increased number, devastated entire populations of algae (consumer of CO2, one of the responsible of global warming), seals who found refuge in the algae nonexistent now were more hunted by killer whales… the sea otter is therefore a key species for the balance of this ecosystem and the planet, as it has evolved along with urchins and algae.

Coevolutive relations between flowers and animals depend on the pollination of thousands of species, including many of agricultural interest, so we must not lose sight of the seriousness of the issue of the disappearance of a large number of bees and other insects in recent years. A complex case of coevolution that directly affects us is the reproduction of fig.

TO SUMMARIZE

As we have seen, coevolution is the evolutionary change through natural selection between two or more species that interact reciprocally.

It is needed:

• Specificity: the evolution of each feature of a species is due  to selective pressures of the feature of the other species.
• Reciprocity: features evolve together.
• Simultaneity: features evolve simultaneously.

REFERENCES

• Massa R (2007). Atlas ilustrado del origen de la vida: La evolución de las especies. Jaca Book spa, Milano.
• Muchhala N. Nectar bat stows huge tongue in its rib cage. Nature (2006) vol. 444 (7120) pp. 701-702
• Coevolución: patrones y procesos
• Celebrando a Darwin
• Los 10 mamíferos más rápidos de la tierra
• La coevolución y las enseñanzas de Darwin
• Coevolución
• Las nutrias marinas pueden salvar nuestro planeta

Dogs made us more sapiens

Look at the dog resting at your side as you read this article or the Yorkshire Terrier that you‘ve seen in the street. French Bulldog, Pug, Chihuahua, West Highland, Golden Retriever, Pinscher… sometimes it’s hard to think that the ancestor of all these races is the wolf. It is known that the variety of breeds of current dogs is due to artificial selection by humans, but the debate is still alive when trying to answer questions about where, when, how and why it occurred domestication of wolves. Have dogs influenced our evolution as a species? Why do we have such a close relationship with them?

HIPOTHESES ABOUT THE ORIGIN OF THE DOG

Currently it is known that the ancestor of the dog is the wolf (Canis lupus), probably of some extinct species. The dog (Canis lupus familiaris) is in fact one of the two domestic subspecies of the wolf; the other is the Australian dingo (Canis lupus dingo) although it is considered wild nowadays.

Eurasian wolf (Canis lupus lupus). Photo by Bernard Landgraf.

The first hypotheses that attempt to explain the origin of the dog, were based on the idea that our ancestors caught wolf cubs and raised them as pets. But since domestication is a slow and long process, this belief is now ruled out. What tell us the most recent researchs?

• A research in 2002 argued for an Asian origin (China today) 15,000 years ago, based on analysis of mitochondrial DNA from more than 600 dogs.
• Another researh in 2010  placed the origin of the dog about 12,000 years ago in the Middle East, based on fossils.
• In 2013, a mitochondrial DNA analysis of prehistoric canids, modern dogs and wolves concluded that domestication occurred between 18,800-32,100 years ago in Europe, much earlier than previously thought. The dog would be then the first living being domesticated by humans, since its origin predates agriculture. This would cast serious doubts in the same year’s rechearch telling that some wolves were able to metabolize starch, and therefore the cereals of early farmers, which favored (among other things) the rapprochement between wolves and humans.

The Razboinichya canid, a 33.000 years old fossil with evidence of domestication. Photo taken of Plos One.

Agriculture and ranching surely influenced the evolution of the dog, but the contact between humans and wolves was when we were hunters and gatherers, before the domestication of animals more profitable (cows, sheep …). But how did it happen?

THE WOLF WAS DOMESTICATED ITSELF

The domestication of the wolf is unique because it is the only large carnivore in which we have succeeded. As reported by Science in April 2015, most scientists believe that were the wolves who approached human settlements voluntarily. Those who were less timid, more easily obtained food from the remains of dead animals left by our ancestors. Over time, these wolves survived longer and each generation was slightly different to previous, less and less fearful of humans. Humans would choose the most docile up to live with them. Wolves’ social skills and cooperation with its kind were maybe features that helped to cooperation with humans.

Neolithic burial of a woman and a dog, Ripoli (Italia). National Museum of Antiques of Chieti. (Credits)

Over thousands of years the relationship between humans and dogs has been coevolution (one has influenced the evolution of the other and vice versa), so much to create bonds with just a look, something  that we might think that is a exclusive hominid feature. When you look into the eyes of your dog the same hormone is released in both (oxytocin), the same hormone that is released when a mother looks at her son. If you also have the feeling that your dog understands you when you look at it, you smile at it, you talk to it … apparently you’re not entirely wrong.

CONSEQUENCES OF LIVING TOGETHER WITH DOGS IN HOMO SAPIENS

Althought your dog is just a pet and/or part of your family, they are now also used for almost the same tasks as those already profited early modern Homo sapiens:

• Help for hunting: dogs could track the dam because they have a better smell, pursue and harass it until we killed it if it was too big for them. In addition, it is possible that humans communicated with dogs with his eyes, making a quieter hunting.
• Search for buried or hidden food.
• Transporting objects: fossils indicate that the first dogs carried objects in its backs and pulled carts.
• Monitoring and protection against other predators, through better night vision and hearing.
• Use as alternative food if hunting was scarce.
• After the appearance of ranching, to control livestock.

The dog in turn, also made a profit from its union with H. sapiens, especially in the way of food easy to get.

Cave paintinf inTassili (Argelia) showing a hunting scene with dogs

An important consequence of the domestication of the wolf is that it was the starting point of the domestication of other animals. Our ancestors understood the advantages that supposed to have domesticated animals to their advantage, so the ranching revolution started about 10,000 years ago.

Furthermore, Pat Shipman, antrophologist, has published recently a paper and a book where explains the advantage that H. sapiens with dogs would have had against H. neanderthalensis, even contributing to the extinction of this species. Apparently the advantages set forth above associated with dogs, not only gave the first modern sapiens advantage to compete with other carnivores for food, scarce in full glaciation. Also they had an advantage over the Neanderthals, which had only their own means to feed. Not only disappeared with our arrival the Neanderthal population in Europe, so did the mammoths, European lions and buffalos.

Recreation of a neanderthal camp. American Museum of Natural History. Photo by Mireia Querol

The causes of extinction of the species most similar to ours, the Neanderthals, remain a mystery. The reasons are probably multiple but rarely we ask ourselves that “man’s best friend” has contributed to this. Perhaps thanks to them you’re reading this article and I’m writing it, perhaps we are here as a species thanks to dogs.

REFERENCES

• Los perros se hicieron amigos del hombre escarbando en sus basuras
• Los lobos se hicieron perros siguiendo a los primeros cazadores europeos
• Cómo los lobos se convirtieron en perros
• Historia de la domesticación del perro
• La mirada entre perro y dueño refuerza su unión emocional
• Cover photo (siberian husky) by Mireia Querol

Orchids: different colours and shapes for everyone

The orchid family is composed of a big number of species, about 20.000. Even they are almost around all world, the most live in tropical places and they are epiphytes, that is, they live over other plants. Nowadays, the number of the species is boosted by the commercial interest. Trying to find new characters and colours, many gardeners and hobbyists have created new varieties from the breeding of two distinct species of orchids, that is, they have made artificial hybridization. Even so, it can also happen in nature as usual.

MORPHOLOGICAL CHARACTERISTICS

The orchid flower owns a single structure. The most representative part is the column or gynostemium, which is the result of masculine and feminine reproductive parts combined. The perianth, consisting of the calyx (the outermost whorl of parts that form a flower. Its pieces are the sepals) and the corolla (composed of all of the petals), has free pieces and is zygomorphic (single symmetry plane). A much differentiated petal can be seen, it’s the lip. It adopts a different attractive shape and it can own macules (attractive spots for the pollinators). The lip is also adapted to capture the pollinators’ attention and can possess a long prolongation called spur and it has nectar. The flowers may be accompanied by a bract, a modified or specialized leaf.

Structure of orchid flowers (Photo taken by Gisela Acosta).

The flower development is very singular in some orchids. Some flowers are born backwards and when they are maturing the ovary twist 180º to help flower stay in proper position, being the own ovary who acts as a peduncle, linking flower and stem. This kind of flower development is called resupinate. The flowers can be solitary or grouped in inflorescences.

Resupinate development of flowers (Orchis mascula) (Photo taken by Jonathan Billinger).

The orchids are entomophilous, that is, are pollinated by insects. Depending of the specie, the orchid will be pollinated by a type of insect or other. Even so, this relation or form of pollination (the position in which bees, bumblebees and other hymenoptera get to copulate) cannot be used to describe how evolution happened in orchids; this pollination mechanism was used in the past to classify species, but molecular analyses have denied its worth.

One singular characteristic of tropical species is the velamen radicum: a multi-layered coating on the roots that acts as a sponge. In drought periods this coating protects from the drying and doesn’t allow the losing of water. And in rainy periods, this coating is swollen of water, which will be available to roots. Also, as these orchids are epiphytes, are adapted to drought places.

Epiphytic orchid on a tree (Pleione limprichtii) (Photo taken by Adarsh Thakuri)

Orchids live in mutualism with fungus, that is, they establish a relationship in which both organisms are benefited when live together. The orchid seeds need the fungus’ aid to germinate. Many several fungus can stimulate their germination, but  Rhizoctonia (Basidiomycota) is predominant. The fungus degrades the seed coat and releases of dormancy period. Then, the seed begins to germinate and emits filaments, underground organs, and establishes an orchid mycorrhizae. The seed dormancy can last 20-30 years without germinating, but it will not be possible without the fungus action.

DIVERSITY

Within the great diversity of orchids, some flowers of diferent species create such original shapes that they seem animals, such as monkey orchid (Orchis simia), or insects, such as genus Phalaenopsis; their flowers supposedly resemble moths in flight, and that’s why they are known as the moth orchids.

On the left, monkey orchid (Orchis simia) (Photo taken by Ian Capper); On the right, orchids that resemble moths in flight (Phalaenopsis schilleriana) (Photo taken by Amos Oliver Doyle).

The bee orchids (Ophrys), for example, have a specialized lip that can really attract the hymenopterans. It’s because it reminds female shape and colours and it also emits smells which are similar to female pheromones, doing the pollination more effective.

Bee orchid (Ophrys apifera) (Photo taken by Hans Hillewaert).

On the other hand, there are also many curious cases like the Darwin’s orchid (Anagraecum sesquipedale). It’s characterized by its long spur between 25 and 35 cm in length. Darwin guessed it should exist a butterfly that could take the nectar located in the spur and pollinates the flower at the same time. Xanthopan morgani is able and it’s the only one, so it’s one coevolution case.

On the left, Darwin's orchid (Anagraecum sesquipedale)(Photo taken by Michael Wolf); On the right, Xanthopan morgani (Photo taken by Esculapio).

We can also see species with a high ornamental value, being the most of them from Asia and America. For example, the Cattleya genus has one of the highest floral value and it was used extensively for create new varieties. So, Cattleya has become very popular until today.  A good example is the easter orchid (Cattleya mossiae), which is also the national flower of Venezuela.

Easter orchid (Cattleya mossiae) (Photo taken by KENPEI).

When we speak of floral value, we can’t forget Rothschild’s slipper orchid (Paphiopedilum rothschildianum). It’s the most expensive orchid in world and it’s considered one of the most expensive flowers, too. Rothschild’s slipper orchid only lives in Mt. Kinabalu, on the island of Borneo, and it’s also one of the rarest orchids in nature of all of the species of Asian Slipper orchids.

Rothschild's Slipper Orchid (Paphiopedilum rothschildianum) (Photo taken by Orchi).

Furthermore, orchids are important in alimentation, being surely Vanilla planifolia the most relevant. It’s native to Mexico and vanilla is obtained of its fruits.

Vanilla (Vanilla planifolia) (Photo taken by Michael Doss).

REFERENCES

The following sources have been consulted in the elaboration of this entry:

• Bolòs, J. Vigo, R. M. Masalles & J. M. Ninot. 2005. Flora manual dels Països catalans. 3ed. Pòrtic Natura, Barcelona: pp. 1310.
• Phanerogamae notes, Degree of Environmental Biology, UAB.
• http://orquideastropicales.com/images/Web%20Preview%20OrqTrop%20Optimizado%20codificado.pdf
• http://tailandia.galeon.com/images/orquid1.gif
• http://www.biodiversidad.gob.mx/Biodiversitas/Articulos/biodiv49art3.pdf
• http://www.lt-wasserthal.de/page8/page18/page18.html
• http://www.theorchidcolumn.com/2013/02/all-hail-paphiopedilum-rothschildianum.html

In conclusion, orchids are important in different aspects and that’s why a biggest knowledge of their diversity and biology is necessary. If you liked this article, wouldn’t forget to share it. Thanks for your interest.

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