Category Archives: Conservation

Friday Fellow: Rhinoceros Tick

by Piter Kehoma Boll

Parasites exist everywhere and, although most of us see them as hateful creatures, more than half of all known lifeforms live as a parasite at least in part of their life. And there are likely many more yet unknown parasites around there. Today I’m going to talk about one of them, which is found in large portions of Africa.

Its name is Dermacentor rhinocerinus, known as the rhinoceros tick. As its name suggests, it is a tick, therefore a parasitic mite, and its adult stage lives on the skin of the white rhinoceros (Ceratotherium simum) and the critically endangered black rhinoceros (Diceros bicornis).

A male rhinoceros tick attached to the skin of a rhinoceros in South Africa. Credits to iNaturalist user bgwright.**

Male and female rhinoceros ticks are considerably different. In males, the body has a black background with many large orange spots. In females, on the other hand, the abdomen is mainly black with only two round orange spots and the plate on the thorax is orange with two small dark spots. Males and females mate on the surface of rhinoceroses. After mating, the female starts to increase in size while the eggs develop inside her and then drops to the ground, laying the eggs there.

A female rhinoceros tick patiently waiting for a rhinoceros to come close. Photo by Martin Weigand.**

The larvae, as soon as they hatch, start to look for another host, usually a small mammal such as rodents and elephant shrews. They feed on this smaller host until they reach the adult stage, when they drop to the ground and climb on the surrounding vegetation, waiting for a rhinoceros to pass by and then attaching to them.

Conservation efforts to preserve biodiversity are mainly focused on vertebrates, especially mammals and birds. Rhinoceroses, which are an essential host for the rhinoceros tick to survive, are often part of conservation programs and, in order to increase their reproductive success, the practice of removing parasites from their skin is common. This is, however, bad for the rhinoceros ticks. If their host is endangered, they are certainly endangered too, and removing them worsens their condition. Are parasites less important for the planet? Don’t they deserve to live just as any other lifeform? We cannot forget that nature needs more than only what we consider cute.

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More mites and ticks:

Friday Fellow: Giant Red Velvet Mite (on 22 June 2016)

Friday Fellow: Cuban-Laurel-Thrips Mite (on 28 June 2019)

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References:

Horak IG, Fourie LJ, Braack LEO (2005) Small mammals as hosts of immature ixodid ticks. Onderstepoort Journal of Veterinary Research 72:255–261.

Horak IG, Cohen M (2001) Hosts of the immature stages of the rhinoceros tick, Dermacentor rhinocerinus (Acari, Ixodidae). Onderstepoort Journal of Veterinary Research 68:75–77.

Keirans JE (1993) Dermacentor rhinocerinus (Denny 1843) (Acari: Ixodida: Ixodidae): redescription of the male, female and nymph and first description of the larva. Onderstepoort Journal of Veterinary Research 60:59–68.

Mihalca AD, Gherman CM, Cozma V (2011) Coendangered hard ticks: threatened or threatening? Parasites & Vectors 4:71. doi: 10.1186/1756-3305-4-71

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**Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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Filed under Arachnids, Conservation, Friday Fellow, Parasites, Zoology

Alien invasions: the resistance lies in streams

by Piter Kehoma Boll

Human activities have been introducing, either deliberately or accidentally, several species in areas outside of their native range. Many os these species, when they reach a new ecosystem, can have devastating effects on the local communities.

One common practice is the introduction of exotic fish for food production or recreation. Although the impact of exotic fish species can be severe, there are several factors that modulate this severity. However, one situation in which it can have catastrophic outcomes is when fish are introduced in water bodies that were originally fishless.

Mountain streams and lakes are usually fishless because of physical barriers, especially waterfalls, as they prevent fish from moving upstream. But fish have been introduced in many mountain lakes to provide a local food stock or for sport fishing.

One place that was plagued this way is the Gran Paradiso National Park in the Western Italian Alps. During the 1960s, the brook trout, Salvelinus fontinalis, a fish that is native from North America, was introduced in several of the park’s high-altitude lake. Later, when the area became proteced, fishing was prohibited.

Salvelinus fontinalis, the brook trout. Photo by Alex Wild.

From 2013 to 2017, a fish erradication program was conducted in four lakes of the park, namely Djouan, Dres, Leynir and Nero. Fish were captured using gillnetting and electrofishing. Since the trouts had colonized the streams that are connected to the lakes, they had to be removed from there as well.

The communities of organisms living in the lakes and streams were monitored to assess their recovery after the fish removal. The lakes showed a remarkable resilience, reaching a community structure similar to that of lakes where fish were never introduced. The streams, on the other hand, did not show a great difference before and after fish removal. The reason, however, was not that streams have low resilience. On the contrary, streams showed a great resistance to fish invasion. Trouts did not seem to have affected the macroinvertebrate communities of streams that much. But why is it so?

Dres lake in the Gran Paradiso National Park. Image extracted from the park’s website (http://www.pngp.it).

One hypothesis was that macroinvertebrates constantly colonize the streams by passive dispersion, coming from upstream waters. However, this is not applicable to streams that drain the lakes, as lake and stream communities are very different. Lower predation by trouts is not an option either, because it was shown that stream trouts actually eat more than lake trouts. Maybe stream invertebrates reproduce more quickly than lake ones? No! Studies have shown than this is similar in both environments.

The reason why stream invertebrates are less affected by the introduction of fish is still a mystery. One possible explanation is that streams present more microhabitats that are not explored by the trouts, providing refuges for the invertebrates. We need more studies to understand what is going on.

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You may also like:

Exotic species: are they always a trouble?

The New Guinea Flatworm visits France – a menace

Obama invades Europe: “Yes, we can!”

Think of the worms, not only of the whales, or: how a planarian saved an ecosystem

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References:

Tiberti R, Bogliani G, Brighenti S, Iacobuzio R, Liautaud K, Rolla M, Hardenberg A, Bassano B. (2019) Recovery of high mountain Alpine lakes after the eradication of introduced brook trout Salvelinus fontinalis using non-chemical methods. Biological Invasions 21: 875–894. doi: 10.1007/s10530-018-1867-0

Tiberti R, Brighenti S (2019) Do alpine macroinvertebrates recover differently in lakes and rivers after alien fish eradication? Knowledge & Management of Aquatic Ecosystems 420: 37. doi: 10.1051/kmae/2019029

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Friday Fellow: Portuguese Millipede

by Piter Kehoma Boll

Millipedes, which make up the class Diplopoda, are very cute arthropods in my opinion and include amazing species, such as the animal with the largest number of legs in the world. Many species are not well studied, though. However, one that is very well known is the Portuguese Millipede Ommatoiulus moreleti.

As its common name suggests, the Portuguese millipede is native from Portugal, more precisely from Southern Portugal and nearby areas in Spain, living in the soil of pine and oak forests. Its body, measuring about 4 cm as adults, has the typical cylindrical and elongate shape seen in most millipedes and is very dark, almost black, with legs that have a light color, usually whitish, but sometimes purplish.

A Portuguese millipede in Portugal. Photo by Romulo Arrais.*

Despite its relatively small size, the Portuguese millipede takes more than a year to reach maturity and grow for about three years. The mating period is usually during Autumn, and after having its eggs fertilized, the female lays from 60 to 80 of them in a chamber about 2 cm deep in the soil. When the eggs hatch, the first stage is a small, pupoid legless animal that remains inside a membrane until it molts into a small six-legged larva. During the first year, the juvenile molts about 8 times and the number of legs increases at each new stage. At about stage 10, they are sexually mature, but continue to molt and gaining more legs until reaching about 90 legs at the 14th stage. Males have an interesting reproductive strategy called periodomorphism, in which mature individuals molt into a “castrated” form, with reduced sexual organs, and becomes sexually mature again in the next molt, only to return to the immature form again in the next molt and so on.

The Portuguese millipede became famous after its accidental introduction in southeastern Australia, apparently in the 1950s. It soon became a very abundant species and, as a consequence, a nuisance for humans. As most millipedes, the Portuguese millipede is mainly detritivorous, feeding on dead plant material, such as rotten wood and dead leaves, so its introduction is not that much an ecological catastrophe, although it can have some negative impacts by competing with native millipede species.

A Portuguese millipede in Australia. Photo by iNaturalist user corunastylis.**

The main problems caused by the introduction of the Portuguese millipede in Australia affect mostly humans. They are attracted to weak light sources, such as those emitted by houses at night, and, as a result, end up invading residences, sometimes hundreds of them at a time. When threatened, the Portuguese millipede emits a pungent yellow secretion that can irritate the eyes and, in contact with clothes, mark them with a permanent stain. Addtionally, the Portuguese millipede sometimes can feed on some crops, especially fruits.

In Portugal, the populations of the Portuguese millipede are controlled by native predators, such as the European hedgehog Erinaceus europaeus and the beetle Ocypus olens. Released from these natural enemies, the millipede spread quickly through southeastern Australia. However, about 30 years later, its population in Australia started to decrease. Apparently some nematode parasites that infect native millipedes adapted to parasitize this invasive species as well, helping to contain its population size. Some other native Australian predators have also observed feeding on the Portuguese millipede, including the blue garden flatworm, Caenoplana coerulea.

Other than Australia, the Portuguese millipede was also introduced in several Atlantic Islands, such as the Macaronesian Islands, Bermuda and the UK, as well as in South Africa. However, it does not seem to be that much of a nuisance there.

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More millipedes:

Friday Fellow: Leggiest Millipede (on 12 February 2016)

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References:

Baker GH (1985) Predators of Ommatoiulus moreletii (Lucas) (Diplopoda: Iulidae) in Portugal and Australia. Australian Journal of Entomology 24(4): 247–252. doi: 10.1111/j.1440-6055.1985.tb00237.x

Baker GH (1978) The post-embryonic development and life history of the millipede, Ommatoiulus moreletii (Diplopoda: Iulidae), introduced in south-eastern Australia. Journal of Zoology 186: 209–228. doi: 10.1111/j.1469-7998.1978.tb03366.x

Gregory SJ, Owen C, Jones G, Williams E (2018) Ommatoiulus moreleti (Lucas) and Cylindroiulus pyrenaicus (Brölemann) new to the UK (Diplopoda, Julida: Julidae) and a new host for Rickia laboulbenioides (Laboulsbeniales). Bulletin of the British Myriapod & Isopod Group 30: 48–60.

McKillup SC, Allen PG, Skewes MA (1988) The natural decline of an introduced species following its initial increase in abundance: an explanation for Ommatoiulus moreletii in Australia. Oecologia 77:339–342. doi: 10.1007/BF00378039

Terrace TE, Baker GH (1994) The blue land planarian, Caenoplana coerulea Moseley (Tricladida: Geoplanidae), a predator of Ommatoiulus moreleti (Lucas) (Diplopoda: Julidae) in southern Australia. Australian Journal of Entomology 33(4): 371–372.

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*Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License.

**Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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Instead of toxic chemicals, use helping plants to get rid of crop pests

by Piter Kehoma Boll

Finding efficient ways to deal with agricultural pests in crops is a challenging work. Currently, as we all known, the main strategy to control such pests is the use of chemical pesticides. However, this approach only serves the interests of those seeking profit over well-being, as we all know that such pesticides increase the risk of several health issues in those consuming the crops. More than that, chemical pesticides not only kill the targeted pest but many other life forms, causing a devastating effect on ecosystems.

The cross-striped cabbageworm (Evergesis rimosalis) is a common pest in plants of the genus Brassica (kale, cabbage, mustard) in the eastern United States. Photo by iNaturalist user margaridamaria.*

Fortunately, there has been an increasing interest in finding alternative, healthier ways to deal with the problem. One way is the production of genetically modified organisms (GMOs) that are naturally resistant to pests. There are, however, two main problems with this approach. The first one is that the population in general has an irrational fear of GMOs, apparently believing that they can be more harmful than the poisonous chemical pesticides, which is completely absurd. The second problem with GMOs is that the technology to create them is dominated by the same companies that produce most pesticides and, as all big companies, only seek profit and do not give a damn about the people and the environment.

A third strategy is the use of natural enemies of the pests to control them in organic farms. Although many natural enemies are great doing their job, they may also cause negative impacts by interfering with the surrounding ecosystems. Many crop pests are not native from the area where they are pests, i.e., they are invasive species and, in order to control them efficiently, a predator from its native area must be introduced as well, and this predator may end up becoming a threat to other species that it elects as food.

Coleomegilla maculata is a common predatory lady beetle in the eastern United States. They are great to control agricultural pests locally but should not be deliberately introduced elsewhere. Photo by Riley Walsh.*

Fortunately, some nice strategies have been recently developed. One of them includes the use of additional plants in the fields that change the way that pests behave without posing a threat to surrounding areas. These additional plants consists of two types: trap crops and insectary plants.

The common buckwheat Fagopyrum esculentum has been used as an insectary plant. Photo by iNaturalist user jimkarlstrom.*

A trap crop, as the name suggests, is an additional crop that is not intended to be commercially exploited, but serves as a trap for the pests. Instead of attacking the main crop (called the ‘cash crop’), the pests are attracted to the trap crop, reducing their density in the cash crop. This system is more efficient if the trap crop is similar to the cash crop, such as another plant of the same genus, or another variety of the same species, because it must be as attractive to the pest as the cash crop, or perhaps even more attractive.

Insectary plants, on the other hand, are intended to attract other insects to the plantation, especially predatory insects that prey on the agricultural pest. Insectary plants should produce flowers in abundance, thus attracting many insect species, which will increase the interest of predators in the area. However, when used alone, insectary plants will only provide predators to control the pest in crop plants that are near the insectary plants and, as they are usually planted in an area surrounding the plantation, they would not protect the plants that are near the center of the plantation.

In a recent study, Shrestha et al. (see references) decided to combine trap crops and insectary plants together with the cash crops in a strategy that they called a ‘botanical triad’. The cash crap was organic cabbage (Brassica oleracea var. capitata) planted in the eastern United States; the trap crops were three other crops of the genus Brassica: mighty mustard (Brassica juncea), kale (Brassica oleracea var. acephala) and collard (Brassica oleracea var. italica); and the insectary plants were buckwheat (Fagopyrum esculentum) and sweet alyssum (Lobularia maritima).

Kale (Brassica oleracea var. acephala). Photo by David Adreas Tønnessen.*

As a result, the number of herbivores (i.e., crop pests) was larger in the trap crops than in the cash crop. The trap crops were, therefore, more attractive than the cash crops for the pests. The presence of insectary plants increased the number of predatory and parasitoid insects, such as lady beetles and parasitoid wasps, in the trap crops when compared to treatments without insectary plants. The number of parasitized pests also increased in the presence of insectary plants.

Field layout of the study by Shrestha et al. (2019).**

In general, the “team work” of trap crops and insectary plants greatly reduced the influence of agricultural pests on the cash crops. The trap crops attracted the pests to an area close to the insectary plants, allowing the predators to reach them.

Efficient ways to raise crops organically are possible. We just have to focus on a healthy ecosystem and not on money. If we work together, we can defeat the “Big 6” corporations that dominate the food production in the world. They are the real pests.

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Reference:

Shrestha B, Finke DL, Piñero JC (2019) The ‘Botanical Triad’: The Presence of Insectary Plants Enhances Natural Enemy Abundance on Trap Crop Plants in an Organic Cabbage Agro-Ecosystem. Insects 10(6): 181. doi: 10.3390/insects10060181

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*Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

**Creative Commons License This work is licensed under a Creative Commons Attribution 4.0 International License.

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Green turtles mistake plastic debris for dead squids, eat them, and die

by Piter Kehoma Boll

Plastic pollution is a popular topic recently and it is not rare to find pictures of animals that died due to plastic ingestion or other complications, such as asphyxia, caused by plastic pieces. However, the cause of plastic ingestion by most species is yet unknown.

Albatross with its stomach filled with plastic pieces.

The leatherback turtle, Dermochelys coriacea, is often mentioned as a species that suffers from plastic ingestion due to its diet composed primarily by jellyfish, which floating plastic bags can be mistaken for. However, another widespread sea turtle, the green turtle, Chelonia mydas, is also a common victim of plastic ingestion and amounts as small as 1 g are enough to kill juvenile specimens by blocking their guts. The diet of juvenile and adult green turtles is composed mainly by seagrass and algae, so the ingestion of plastic must be the result of another cause and not its similarity to jellyfish.

A decaying plastic bag in the ocean looks like a jellyfish. Photo by Wikimedia user Seegraswiese.*

Despite being almost strictly herbivorous, green turtles ingest animal matter when they are very young and can eventually consume animals as adults too, probably as a strategy to survive when their main food source is scarce. The ingestion of animal matter is usually done by scavenging, and a common scavenged item in their diet are dead squids.

A green turtle surrounded by seagrass, its main food source. Photo by Wikimedia user Danjgi.**

A recent study has investigated the relationship between scavenging behavior and plastic consumption in the green turtle and found out that the amount of plastic ingested by individuals feeding on dead squids is much higher than that ingested by individuals that do not present a scavenging behavior. In Brazil, plastic ingestion accounts for about 10% of the deaths of green turtles but this number may be as high as 67% among green turtles that feed on squid carcasses.

The ingestion of dead animals used to be an efficient way for green turtles to gain high amounts of protein. However, the fact that, currently, most floating material in the ocean is plastic and not dead animals turned a successful strategy into a deadly trap. If humans do not start controlling plastic waste production there will be only two possible outcomes for the green turtles in face of this new selective pressure: adaptation or extinction.

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References:

Andrades R, Santos RA, Martins AS, Teles D, Santos RG (2019) Scavenging as a pathway for plastic ingestion by marine animals. Environmental Pollution 248: 159–165. doi: 10.1016/j.envpol.2019.02.010

Mrosovsky N, Ryan GD, James MC (2009) Leatherback turtles: the menace of plastic. Marine Pollution Bulletin 58(2): 287–289. doi: 10.1016/j.marpolbul.2008.10.018

Santos RG, Andrades R, Boldrini MA, Martins AS (2015) Debris ingestion by juvenile marine turtles: an underestimated problem. Marine Pollution Bulletin 93(1–2): 37–43. doi: 10.1016/j.marpolbul.2015.02.022

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*Creative Commons License This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

**Creative Commons License This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

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Filed under Behavior, Conservation, Extinction, Pollution, Zoology

Antidepressants in wastewater are unbalancing food webs

by Piter Kehoma Boll

Leia em português

Wastewater is one major cause of water pollution on a global scale and this includes domestic wastewater. With the increase in the use of pharmaceuticals of many types to treat a variety of health conditions, these substances end up in domestic wastewater and, even in places with wastewater treatment, such drugs are not always completely removed.

The most commonly detected drugs in aquatic environments include antidepressants. Although in very low concentrations, their effects on organisms are poorly known.

A recent study investigated how the presence of two antidepressants, citalopram (a selective serotonin reuptake inhibitor) and tramadol (a serotonin-norepinephrine reuptake inhibitor) affect the predatory activity of dragonfly nymphs of the species Aeshna cyanea. The insects were exposed to concentrations of about 1 microgram per liter of the substances, a concentration similar to that found naturally in environments affected by wastewaters. Additionally, they used effluents from wastewater treatment plants that included a mix of several drugs in real concentrations.

A nymph of Aeshna cyanea. Photo by André Karwath.*

The results indicate that dragonfly nymphs increase the amount of time they spend searching for food in the presence of the two antidepressants and spend more time handling prey but their feeding rate decreased, i.e., they eat less than nymphs of the control group, i.e., in water without antidepressants. On the other hand, nymphs exposed to effluent from wastewater treatment plants ate more than nymphs of the control group. The exact reason for the opposite effect caused by normal wastewater is unknown, but may be related to the combined effect of several drugs.

Although the effects do not seem to be that problematic at first, an increase or decrease in feeding rate by predators may unbalance the population of the prey species by making it increase or decrease and eventually reach a point that leads to a collapse in the ecosystem.

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Reference:

Bláha M, Grabicova K, Shaliutina O, Kubec J, Randák T, Zlabek V, Buřič M, Veselý L (2019) Foraging behaviour of top predators mediated by pollution of psychoactive pharmaceuticals and effects on ecosystem stability. Science of The Total Environment 662: 655–661.

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*Creative Commons License This work is licensed under a Creative Commons Attribution-Share Alike 2.5 Generic License.

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Friday Fellow: Leatherleaf Fern

by Piter Kehoma Boll

Leia em Português

You may have seen parts of today’s fellow at least once in your life, as it is a very popular plant in flower arrangements.

A flower bouquet including leaves of Rumohra adiantiformis.

Rumohra adiantiformis is how it is known by botanists, and common names include leatherleaf fern, seven-weeks fern and iron fern. This fern species is widely distributed in Australasia, southern Africa and the Neotropics, as well as several islands of the Pacific Ocean.

Living in forested areas, especially where there is not too much shade, the leatherleaf fern has a biology that is not very different from that of other ferns. It usually grows on the soil, although it may eventually occur on rocks or on trees. What makes this fern special is that its mature fronds are somewhat hard and, after being cut off, continue to have a green and live appearance for a very long time, usually several weeks. This amazing resistance to wilt makes it an ideal species to be used in flower arrangements.

Leatherleaf fern growing in South Africa. Photo by Wikimedia user JMK.*

Currently, most of the leatherleaf fern’s production for commercial use occurs in the state of Florida, USA, where it is cultivated in irrigated shaded nurseries. Other large producers are South Africa and Brazil, especially southern Brazil, but in these two countries the plant is exploited through extractivism, i.e., it is harvested in the wild and not cultivated. Although the extraction of the leatherleaf fern is a widespread activity in both South Africa and southern Brazil and is a major source of income for many families, it is illegal under national or regional laws. However, at least in southern Brazil, where the leatherleaf fern occurs in the highest recorded densities in the world, the main reason for its populations to be diminishing does not seem to be its extraction but rather natural forest succession. As forests grow older and become darker, they become unsuitable for the leatherleaf fern to grow.

It is, of course, necessary to establish limits for its harvest. Otherwise, its increasing demand in the florist market may end up causing concerning effects on its occurrence. The best alternative continues to be cultivating the fern, as it protects wild populations and allows the harvest of high-quality fronds and a faster recovery after defoliation.

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References:

Geldenhuys CJ, van der Merwe CJ (1988) Population structure and growth of the fern Rumohra adiantiformis in relation to frond harvesting in the southern Cape forests. South African Journal of Botany 54(4): 351–362.

Milton SJ (1987) Growth of Seven-weeks Fern (Rumohra adiantiformis) in the Southern Cape Forests: Implications for Management. South African Forestry Journal 143: 1–4.

Souza GC, Cubo R, Guimarães L, Elisabetsky E (2006) An ethnobiological assessment of Rumohra adiantiformis (samambaia-preta) extractivism in Southern Brazil. Biodiversity and Conservation 15: 2737–2746. doi: 10.1007/s10531-005-0309-3

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