Cactus by Dan Torre (Reaktion Books, 2017), which is essentially a social history of cacti, is the most recent book I’ve finished reading. Unfortunately,
at the rear. I decided to do more research because it piqued my attention.
About 1750 plant species make up the New World genus known as the cactus family.
The four subfamilies that make up the cactoids (including the common stem cacti, and
the opuntioids (the prickly pears, which make up around 75% of the species), the Pereskia (17 species, separated into two groups), and the Maihuenia (two species). In order to further understand the classification of cactus, a group was formed in 2012.
DNA analysis of the cacti’s traditional morphological classification scheme
taxonomists. Early findings indicate that more than half of the examined species do not
the other species in the same subfamily share common ancestors, hence there will be significant
Cacti share a number of physical and physiological characteristics that define them as cacti.
Most people think of cacti as having thorns and living in a desert, although not all species do.
Where orchids flourish, there are many cactus and plants with thorns. Like any substantial, intricate
They are particularly interesting because there are so many variations on the theme of family.
Since cactus fossils are unknown, determining their timing and location requires some
guesswork. Africa does not contain any cactus, so they must have developed after the
Gondwana broke split approximately 120 million years ago. new genetic research
Research on population radiation also indicate that the family has only recently appeared.
emerging for the first time between 30 and 35 million years ago, most likely in southern South America.
The cactus family is said to have descended from scrubby trees from a
It’s likely that the rate was accelerated by the continent’s uplift as the Andes started to emerge.
of species development within cacti. Previously, the Amazon River discharged into the Pacific Ocean,
nonetheless, the Andean uplift reversed that flow with an immense force around 15 million years ago.
Much of Amazonia is developing freshwater lakes. the river channel that exists today
Approximately 10 million years ago, the inland lake vanished. The climate dropped.
Further north, Central America was working to span the North Atlantic.
as well as South America. the shifting of tectonic jigsaw pieces that
represents the limited regions of Central America, the Caribbean, and Mexico.
only the final merging of the continents over a period of 100 million years
The geographical mass that is now Panama formed roughly five million years ago.
Cactus migration into North America has therefore been fairly quick. that 5 million people
types of prickly pair have spread across the entire country of the United States and into
regions of Canada. Specifically because they don’t exhibit the freeze, the cactoid group
In the arid southwest, opuntioids’ tolerance has trailed behind, although they do
Several more million years will likely pass before they stop radiating out into
Many gardeners express a strong dislike for cacti, especially the spiky ones.
they are resilient and fascinating plants. Learning a little bit more about them
Even the most adamant cactus hater might grow to like them a little bit more.
What is the cactus’ evolution?
Pereskia s.l. was found to be separated into the same clades in a 2011 study that used fewer genes but more species, although it was unable to resolve the members of the “core cacti” clade. The relationships depicted above were agreed to be “the most substantial to date.” [33]
Leuenbergeria species (Pereskia s.l. Clade A) consistently lack two essential stem characteristics that are present in the majority of the remaining “caulocacti”: first, like most non-cacti, their stems start to develop bark early in the plants’ lives; second, they lack stomatastructures that regulate air intake into a plant and, consequently, regulate photosynthesis. Contrarily, caulocacti, such as the surviving species of Pereskia s.s. and several Rhodocactus species, generally delay the formation of bark and have stomata on their stems, allowing the stem the ability to play a significant role in photosynthesis. (The two extremely specialized Maihuenia species make an exception.) [34] [36]
The original cacti are believed to have been tiny trees or shrubs with photosynthesis occurring in their leaves. They were residents of tropical regions that occasionally experienced drought. If Leuenbergeria is a suitable representation of these early cacti, then despite having superficial similarities to adjacent trees, they had already developed water-saving techniques (some of which are present in members of other families in the order Caryophyllales). These included the ability to react quickly to periods of rain and minimizing transpiration by making excellent use of water during photosynthesis. The latter was accomplished by closely regulating the stomata’s opening. Early relatives of Pereskia species may have had the ability to change from the typical C3 mechanism, in which carbon dioxide is continuously used in photosynthesis, to CAM cycling, in which carbon dioxide produced during respiration is stored for use during photosynthesis when the stomata are closed. [10]
The evolutionarily significant shift toward stems serving as photosynthetic organs can be seen in the group that includes Rhodocactus and Pereskia s.s. Stomata are present in stems, and bark develops later than it does in typical trees. The “core cacti” exhibit multiple leaf losses that are more-or-less total in the Cactoideae and a continuous rise in stem succulence and photosynthesis. Whether the transition to full CAM photosynthesis in stems occurred separately in Opuntioideae and Cactoideae, in which case it never developed in Maihuenia, or whether it occurred once in the core cacti, in which case it has been lost in Maihuenia. [10]
This article’s “Phylogeny”-related sections need to be updated. Please contribute to updating this article with new information or recent events. (May 2021)
Evolutionary history
Cacti have no fossilized remains that could shed light on how they evolved. [40] Cacti’s global range, however, provides some proof. Cacti are plants native to South America and primarily the southern areas of North America, with the exception of Rhipsalis baccifera, which has only recently expanded to parts of the Old World. This indicates that the family must have originated following the division of the once-common continent Gondwana into South America and Africa during the Early Cretaceous, some 145 to 101 million years ago. [41] It’s less known exactly when cacti evolved after this divide. Older data point to an early origin that occurred in the Late Cretaceous period 9066 million years ago. The origin may have occurred considerably more recently, maybe in the very Late Eocene to Early Oligocene periods, about 3530 million years ago, according to more recent molecular analyses. [40] [42] According to the cacti’s phylogeny, the Leuenbergeria cactus may have originated in Central America and northern South America, but the caulocacti, which have stems that are more or less succulent, evolved later in the southern region of South America before migrating north. [34] It is thought that core cacti, which have firmly succulent stems, first appeared about 25 million years ago. [40] Uplifting in the central Andes, around 2520 million years ago, which was connected to rising and fluctuating aridity, may have served as a catalyst for their evolution. [34] Other succulent plants, such as the Aizoaceae in South Africa, the Didiereaceae in Madagascar, and the genus Agave in the Americas, appear to have diversified at the same time, which coincided with a global expansion of arid environments. However, the current species diversity of cacti is thought to have arisen only in the last 105 million years (from the late Miocene into the Pliocene). [40]
Where did the spines on cacti originate?
It’s not always a good idea to touch cacti with your bare hands. The symbols of plant defense mechanisms are these spiky plants. The modified leaves and bud scales that make up cactus spines. Primordia, a group of cells that give rise to them, are essentially identical to leaf primordia in appearance. Cactus spines, however, are not composed of living tissue like leaves. In these cells, the genes that produce leaves are turned off, and the genes that produce wood fibers are amplified, resulting in the hard structures that many of us have had to pull out of our skin.
It is simple to believe that spines serve only as barriers. They undoubtedly work for a lot of species. Spines also provide another crucial function for many other species, which is to produce shade. The fact that cactus frequently have diminished or no spines when growing in overcast highlands and rainforests serves as an illustration of this.
Sunburn is a significant problem for cacti living in the world’s sunniest locations. Full sun can harm delicate photosynthetic equipment, and strong UV rays can wreak havoc on the genome. Therefore, it is advantageous for any modification to provide some level of protection for these delicate tissues.
The cactus’ spines help protect it from extreme temperature changes. Consider the cactus’ papery or fuzzy spines as a kind of blanket. The air immediately surrounding the cactus is separated from the chilly nocturnal air in these desert environments by these spines. As the sun sets in the desert, temperatures can dip rather low, making this insulation useful.
The ability of spines to collect and distribute water toward the plant’s base is another advantage. In these settings, rain is frequently in short supply, so cacti must be prepared when it does. Water gathers on the spines before draining to the base. They also serve as dew traps, collecting water vapor on their surfaces. Cacti are able to utilize every last drop of water by doing this.
Many of these shade plant spines are too flimsy and flexible to prevent a hungry herbivore, despite the fact that they undoubtedly provide some protection. Secondary compounds play a role in this. Some cactus are incredibly harmful to herbivores, which makes sense. Cacti spines have succeeded in capturing our attention, whether it is for shade, protection, or water collection, and understanding their purpose makes these plants much more astounding.
How Are Cactus Adapted To Survive In A Desert?
Cacti have unique adaptations in their stems, leaves, and roots that allow them to survive in desert conditions. Among these modifications are:
- In order to minimize water loss through transpiration, leaves are reduced to spines.
- Wide and deep roots can collect surface rains and access deep subsurface water.
- To prevent water loss, stomata are recessed.
- Stems with a waxy coating help to retain water and are fleshy and thick to store water and carry out photosynthesis.
How does cactus growth occur?
Birds, wind, and rain all disperse cactus seed. A cactus plant can produce a million seeds over the course of its lifetime, but only one or two of those seeds will germinate into a new cactus. Some cacti reproduce asexually, without seeds or flowers, while others reproduce sexually.
How do cacti alter with time?
Cacti species have evolved to produce spines rather than leaves in order to survive in scorching desert environments. This lessens the surface area of the plant and minimizes the amount of water lost through evaporation. The lava cactus is one of the first species to colonize the exposed volcanic rock on a new island in the Galapagos where freshwater is scarce by successfully adjusting to the environment.
Adaptation takes place when:
- A species is introduced to a new environment or the environment changes.
- A species can endure in the altered habitat for a sufficient amount of time to adapt.
- A species’ genetic diversity makes some members of the population more genetically suited to the altered environment than others.
How did cacti develop?
Succulent plants are the outcome of independently evolving plant families that, via convergent evolution, have adapted to arid environmental conditions all over the world. When creatures from distinct evolutionary lineages develop similar adaptations under similar environmental conditions, this is known as convergence.
What three adaptations do cacti have?
A cactus may endure in the desert because it has the following characteristics: I It has lengthy roots that bury themselves deeply in the ground to capture water. (ii) In order to reduce water loss through transpiration, the leaves have spines. (iii) To hold onto water, the stem of the plant is wrapped in a thick waxy covering.
Why are cacti so painful?
Cactus spines are modified leaves that resemble needles. Cactus may lose less water in hot and arid environments because of its needle-like adaptability. Additionally, they give out some shade and are a fantastic deterrent to animals that might try to eat them.
Some cactus feature camouflage-producing spines, which further helps to defend them from predators who could try to consume them. Less light reaches the stem of the plant because the cactus spines reflect light (reducing water loss).
What types of cactus spines are there?
Various cactus plants may have one of a few different types of cactus spines. Some spine types could be more difficult to remove and hurt more when pricked. Types of cactus spines include:
- tiny, hair-like spines (such as in genus of Cephalocereus)
- Stiffened spines (such as in Mammillaria gracilis)
- rounded spines (such as in Sclerocactus papyracanthus)
- Glochids (such as in Opuntia rufida)
- bent spines (most cacti)
One of the sorts of cactus spines that causes the most discomfort is the glochid. This is due to the glochids’ brittleness and easy skin-breaking. This makes removing them from the skin extremely difficult.
This also applies to cholla or barbed spines. They are extremely painful and easily penetrate skin and soft tissues. These cacti belong to the Opuntioideae subfamily, which also includes Chollas and Cylindropuntia.
Because they adhere to flesh, clothing, and fur with ease, cholla cacti are sometimes known as jumping chollas. They must be carefully removed from the skin since if done by hand, they would cling to the fingers.
How old are cacti on the planet?
The majority of plants from the New World are cacti. This indicates that only North America, South America, and the West Indies are home to them. Rhipsalis baccifera, a species with a pantropical distribution that can be found in tropical America as well as Old World tropical Africa, Madagascar, and Sri Lanka, is the sole exception. This plant is believed to have only recently colonized the Old World (within the last few thousand years). Its seeds were likely transported there by migratory birds. After being introduced by humans to comparable habitats in other regions of the world, many additional cacti have naturalized there.
It is thought that cacti have just been around for the past 30–40 million years. The Americas were once connected to the other continents, but continental drift caused them to separate. The New World’s distinctive species must have evolved after the continents split apart. Only in the last 50 million years have the continents moved significantly apart. The fact that the continents had already separated when cactus developed may help to explain why they are so uncommon in Africa. Many succulent plants, both in the Old and New Worlds, resemble cacti greatly and are frequently referred to as “cactus” in everyday speech. However, none of these are closely linked to the Cactaceae and this is because of parallel evolution.
In order to create a cochineal dye industry and serve as a natural agricultural fence, prickly pears (genus Opuntia) were brought to Australia in the 19th century. However, they soon spread like wildfire and became a major weed. For local herbivores, this invasive species is toxic, and it has rendered 40,000 km2 of arable ground unusable.