Invsiveness of Lantana camara (West Indian Lantana)

Invsiveness of Lantana camara - The Flowers of Lantana camara Invasive Shrub
The Flowers of Lantana camara Invasive Shrub

The Invsiveness of Lantana camara largely compensates for the ornamental character of the plant. Where thanks to this abominable invasive capacity it has made itself a very serious problem in most areas of the planet that have been tested by its invasive prowess.

The consequences of such action are many and touch many sectors of economic, agricultural, ecological, environmental and social interest. All of this will be discussed later, however, it can only be mentioned at this point that Lantana camara has been declared by the International Union for Conservation of Nature (IUCN) as one of the 100 most harmful weeds worldwide.

Of course, it is fortunate that in recent years more and more sterile ornamental varieties of the plant have become available – however this does not negate the current reality as well as its invasive history.

PS

Consistent with the inconsistency of our announcements, we hereby renege on our pledge not to be published relatively soon a tribute to the nasty and annoying invasive side of the plant.

But, dear reader, don’t worry, because we don’t: after all the editorial team of "Kalliergeia" announces from this very platform its strong commitment to an additional tribute to the management and fight against the West Indian Lantana as a weed, also relatively soon.

Which offers the members of the "Kalliergeia" editorial team the opportunity to reflect on the meaning of time and its reception by man – even if the latter may be the worst reflective one as a member, alas, of the aforementioned editorial team.

The great adaptability of the West Indian Lantana allows it to invade a variety of environments that are quite different from each other.

Infestation by Common Lantana-© Forest and Kim Starr, Starr Environmental, Bugwood.org
Infestation by Common Lantana-© Forest and Kim Starr, Starr Environmental, Bugwood.org
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Introduction History of Lantana camara in the Old World & Elsewhere

After the cosmogonically important discovery of the shortest (?) sea route from Europe to China and India – the work of the greatest explorer and seafarer Christopher Columbus, the son of  Domenico and Susanna, the genus Fontarossa – and the unfortunate intervention of the American continent, from the last was introduced multitude of new plant and other species in the Old World.

One of them was the West Indian Lantana, which is widely believed to have been brought to Europe, probably from Dutch Brazil at the time by Dutch explorers, in the 4th decade of the 16th century CE (perhaps 1636).

The plant has since been systematically cultivated in greenhouses, and thanks to its abundant and attractive flowering, it has spread both to the rest of Europe and to Asia and Oceania for purely ornamental purposes.

But because any job is a blessing (??), Lantana camara, taking advantage of the favorable conditions it found in its new environments, worked tirelessly to spread further of its own accord, eventually making its species one of the most successful weeds of all time.

Invsiveness of Lantana camara (West Indian Lantana)

Invasiveness of West Indian Lantana on a Hillside in Australia
Invasiveness of West Indian Lantana on a Hillside in Australia

Taxonomic Information & Genetic Background of Lantana camara

Although there are few species of the Lantana genus that were introduced, improved and cultivated in Europe and subsequently spread worldwide, on the contrary, there are not a few varieties of the Lantana camara species that received similar treatments and experienced similar routes.

Thus, it is not at all a strange phenomenon that L. camara now appears as an extremely morphologically differentiated species, if both the breeding efforts of the last 3 centuries and the successive natural crossings and hybridization of its plants within the invasive areas are taken into account.

A consequence of this is the fact of the high genetic diversity of the plant populations. The genetic diversity is reflected in its ploidy levels, since the species has diploid (n = 22), triploid (n = 33), tetraploid (n = 44) and pentaploid (n = 55) varieties. The differentiated ploidy expresses to a significant degree the invasive potential of the West Indian Lantana.

The extent of the plant’s morphological variation results in the (problematic) recording in the L. camara complex of numerous forms, cultivars, biotypes, subspecies and varieties. As for the varieties today they reach about 650. Varieties are classified on the basis of morphological, physiological and genetic differences.

The morphological differences mainly concern:

  • The size, shape and color of the flower
  • The size, color, and hairiness of the leaves
  • The spininess of the stem

Physiological differences concern growth rates and the degree of toxicity in animals and livestock, while genetic differences concern the number of chromosomes and the overall DNA content.

Invsiveness of Lantana camara (West Indian Lantana)

The Global Spread of the Invasive Lantana camara

The L. camara can boast that it has spread spontaneously to more than 65 countries, which are mainly located in the zone between 35°N and 35°S latitude. In some of these countries its invasive potential is small or relatively small and in others it is incredibly large.

It has created serious problems:

  • In India, where it has invaded about 13.2 million ha
  • In Australia, where it has invaded about 4 million ha
  • And in South Africa, where it has invaded about 0.55 million ha

Of great interest is the fact that the spread of the plant continues, since new countries are added to its invaded territory, but even in those where it has been established since the 19th century CE, it continues to becomes overpopulated and harms new areas.

Introduction Year into Countries & Administrative Regions

For the countries and administrative regions in which the year of introduction of the West Indian Lantana is known, a relevant table follows immediately below.

COUNTRY/REGIONYEAR OF INTRODUCTION
Azores 1934
Egypt 1871
Australia 1841
Zimbabwe 1937
USA 1793
Japan 1865
India 1807
China 1645
Corsica 1996
Madeira 1967
Bhutan 1999
New Caledonia1863
Nepal 1848
South Africa1858
Portugal 1967
Singapore 1851
Taiwan 1903
Tahiti 1853
Hong Kong1851

Invsiveness of Lantana camara (West Indian Lantana)

The Habitats of Lantana camara

A plant with the invasive characteristics of the West Indian Lantana cannot but possess a wide adaptability to a variety of ecological, climatic and soil types. And indeed it is, since populations of L. camara can survive in numerous habitats that differ greatly from each other. Furthermore, it has even been suggested that since for its expansion a marginal area lacks plant natural enemies, then climatic and territorial factors play a minimally important inhibitory role. The same seems to be true of maximum temperature values as well as maximum annual rainfall – provided the soils have adequate drainage.

Privileged areas for the invasive action of the plant are primarily disturbed and degraded. And such are:

  • The pastures that have been overgrazed
  • Parts of tropical forests that have been stripped by irrational logging, fires, severe storms, and the natural death of trees
  • The edges of tropical forests
  • The edges of roads, railway tracks, waste places, stripped riparian zones of rivers and streams, and the sides of irrigation canals
  • Coastal areas stripped for various reasons

Also, the L. camara can invade tree or shrub plantations, mainly in tropical areas.

Invsiveness of Lantana camara (West Indian Lantana)

West Indian Lantana Shrub Threat in Sajjangarh, India
West Indian Lantana Shrub Threat in Sajjangarh, India

The Reproduction of L. camara

The plant reproduces both sexual and asexual. Through sexual reproduction and seeds it manages to invade new areas, while through asexual it mostly manages to expand into areas where it is already established.

Sexual Reproduction

The L. camara is definitely a cross pollinating plant. It may even be able to self-fertilize, but research on this topic has, for now, come to conflicting conclusions.

For the pollination of the plant, insects (lepidopteran and thrips) are the main pollinators, followed by birds (species of the families Nectariniidae and Trochilidae – sunbirds and hummingbirds respectively). Of the insects, it seems that it is mainly thrips that carry out the pollination work. The explanation given is that indeed thrips, unlike butterflies (lepidoptera), can be active all year round, and also that they are more efficient pollinators.

A consequence of the pollination is that each plant of West Indian Lantana shows fruit set that reaches a rate of approximately 85%. Each infructescence bears about 8 fruits, and each fruit contains up to 2 seeds at most. In total each plant can produce more than 12000 seeds per year.

Asexual Reproduction

The plant has the ability to produce adventitious lateral shoots, and primarily superficial lateral roots. Superficial roots play an important role in plant extension and regeneration, as they are capable of producing new shoots and plants – especially if they suffer intentional or non-mechanical damage.

Through this specific mechanism and in combination with the production of allelopathic substances (which will be mentioned later), L. camara not only consolidates its presence in the specific habitats in which it has settled, but also creates dense populations, which do not allow the development of other native species, thereby reducing the biodiversity of the ecosystems it invades.

The Dispersal of Seeds

Birds, animals and even reptiles (Galapagos Islands) dispered the seeds of the plant benefiting from the nutritious pericarp.

The birds include Streptopelia chinensis, Acridotheres tristis, Myiarchus magnirostris & Mimus melanotis (the latter two in the Galapagos Islands) inter alia native to each region.

Among animals, sheep, goats, cattle, foxes, jackals, kangaroos, monkeys, and possibly rodents contribute to the dispersal of seeds.

However, in addition to living things, abiotic factors can also play a role in dispersal, as happened in the case of the Ndumo Game Reserve, located in the KwaZulu-Natal province of South Africa: there, in 1983, during of Cyclone Demoina, large quantities of L. camara seeds were transported to its floodplain.

Invsiveness of Lantana camara (West Indian Lantana)

The Germination of Seeds

The germination of the seeds takes place in conditions of intense light and sufficient humidity – conditions which are rarely found beneath parent plants, in order to favor their germination. The optimum temperature is 16 °C.

The germination rate of L. camara seeds is relatively low, ranging between 20 and 49%, both in the laboratory and in the field. Compensating for the relatively low germination rate, the seedlings show an extremely low mortality rate, thus contributing to the cumulative reproduction of the plant.

Invsiveness of Lantana camara (West Indian Lantana)

Allelopathy in West Indian Lantana

Allelopathy & Invasiveness

Allelopathy, in general, is the mutual effect between two plants that are close to each other, which is exerted by the release of a number of secondary metabolites, called allelochemicals. The released in various ways allelochemicals can inhibit the germination and growth of one or the other plant.

Although the existence, role and importance of allelopathy in some plant species is disputed, this does not seem to be the case for L. camara; on the contrary, research shows that it is an allelopathic plant, and even that this characteristic is an essential factor for its dominance in an invasive environment.

The allelopathic compounds of West Indian Lantana include triterpenes, sesquiterpenes, phenolic compounds as well as a flavonoid. Some of these allelochemicals are released into the soil portion under the shrub canopy, and diffuse into the rhizosphere and beyond. They are products of the decomposition process of various types of plant residues, as well as leachates or volatile compounds of some of its living parts.

Consequences of Allelopathy in Habitats & Invaded Areas

The release of L. camara allelochemicals causes a reduction in the vigor and vitality of native plant seedlings that happen to be found in the affected habitats.

So, within the latter, its biochemical dominance in the soil, has as a consequence the gradual population sparsity of native plant species and the density of its own populations. The further increase in the population density of the West Indian Lantana leads to its partial or total dominance and – most of the time – to the formation of impenetrable thickets and compact stands.

In conclusion, it could be said that the larger the population of L. camara plants in a given habitat, the more its severe allelopathic effect is manifested – ultimately resulting in a significant decrease of a stand biodiversity.

Invsiveness of Lantana camara (West Indian Lantana)

Invasiveness of Lantana camara - Infestation by West Indian Lantana-© John M. Randall, The Nature Conservancy, Bugwood.org
Infestation by West Indian Lantana-© John M. Randall, The Nature Conservancy, Bugwood.org

Impacts of the Invasiveness of Lantana camara

The impacts of L. camara invasiveness are large and wide-ranging, involving humans, ecosystems and the environment.

Ecological Impacts

The invasiveness of West Indian Lantana not only negatively affects biodiversity, but also puts endangered plant or animal species at risk of overall extinction.

Enumerating some of them, which are located in different regions of the planet, we will start with the Galapagos Archipelago.

Where the inspired introduction of the plant to the island of Floerana in 1938, by Ainsley and Francis Conway on their small farm, has resulted in the endemic species Lecocarpus pinnatifidus and Scalesia villosa being endangered today by overall extinction.

In the case of the shrub Linum cratericola, for which we do not know the degree of involvement of the above-mentioned small farmers, L. camara is said to be solely responsible for its extinction from the islands of the Archipelago.

In far away (to us) Australia, a large number of endemic plants are threatened by the L. camara relentless advance. Examples include the species Acacia bakeri (one of the tallest Acacias, as it reaches about 40m), the shrubs Boronia umbellata, Hibbertia procumbens, the orchid Pterostylis gibbosa and the fern Drynaria rigidula.

In (not so far away from us) India, the plant bares its teeth on the Bengal Tiger (Panthera tigris tigris), tearing up the feline’s food chain. And it achieves this, since by occupying a significant part of the animal’s habitats, it excludes the development of grazing species for the herbivores, which migrate to more suitable areas, so the carnivore is deprived of its prey.

In Kenya, the candidate victim of L. camara is this time a herbivore, the Sable Antelope (Hippotragus niger). In a somewhat similar situation to the one described a little above, the plant invading the ruminant’s habitat destroys it, not allowing the growth of other plants – grasses or shrubs – suitable for grazing, thus depriving it of food.

Environmental Impacts

The West Indian Lantana contributes to the occurrence of intense fires in tropical dry forests by altering the fire regimes and fuel loads. Without having, most of the time, greater flammability than native species, it nevertheless acts as a fuel to the fire by increasing the amount of combustible material.

This is related to the presence of taller fuel beds, the greater coverage and extent of the invaded areas by the plant, as well as the deposition and creation of thicker leaf litter layers. This is how the fire is fueled and spreads by penetrating the forest.

More generally, the relationship of L. camara with fires seems to be inscribed in a vicious circle, since the regeneration capacity of the tropical dry forest is undermined by it: as the plant has a significant advantage over other native species, it recovers quickly and manifests with aggressively its invasive potential, occupying after each fire more and more forest areas.

In addition to fires, the West Indian Lantana also plays a negative environmental role, this time in terms of absorbing rainwater.

Related research has shown that the invasiveness of the plant, especially in grassland areas, reduces the ability of the soil to absorb rainwater. This means that the amount of runoff water is greater and therefore the risk of soil erosion increases.

Agricultural Impacts

The invasiveness of the West Indian Lantana creates serious problems in the agricultural sector, both in farming and in livestock. About them, a comprehensive report is made immediately below.

Crops

The L. camara affects crops in two ways:

  • Reducing productivity and yields
  • Interfering harvest

It invades perennial crops and plantations becoming a big headache for coconut, rubber, palm oil, citrus, coffee, tea and cotton growers, as well as timber producers.

The countries that face the invasive power of the plant (and are found mainly in Southeast Asia, the Pacific Islands, Oceania, but also in the Indian subcontinent) are:

  • Australia
  • USA (Florida)
  • India
  • Malaysia
  • The islands of Vanuatu, Samoa, Solomon and Fiji
  • The Philippines

Livestock

Livestock is affected by the loss of small or large areas of pastures, as well as by the poisoning of animals. Animals that fall victim to the toxic effect of L. camara are mainly young, which have either been recently introduced into areas invaded by the plant, or have no access to other fodder.

Social Impacts

Not directly but indirectly, the plant also contributes to the exposure of human health to various risks. Its dense stands are prime places for refuge and reproduction of various parasites which are vectors of serious diseases.

These parasites include mosquitoes of the genus Anopheles that carry the protozoa of the genus Plasmodium, namely P. vivax, P. falciparum, P. ovale, P. malariae and P. knowlesi, which are responsible for the disease of Malaria.

In the African countries of Rwanda, Tanzania, Uganda and Kenya, L. camara offers an alternative host option for the 23 species of the Tsetse fly, all of which belong to the genus Glossina, and are the epidemiological vector of the protozoan Trypanosoma, which cause Trypanosomiasis disease.

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References

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From the city of Požega and the 2018 Aurea Jazz Fest, the one and only – though many – Cubismo perform their song Morenita.

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