Top 10 "Keystone Species"

Keystone species are species that, within their own ecosystems, are irreplaceable, or so it is argued. Nothing else within their ecosystem can fill the void if this species were to go extinct. They are considered essential to maintaining the biodiversity of any given ecosystem.

If these species are removed from their particular ecosystems, the system would suffer, fail, or quite possibly collapse. Give these species their proper respect, as they are carrying a lot of responsibility.

Keystone species are not necessarily the top predators within a particular ecosystem, but that is often the case, as these species tend to keep prey animal numbers in check and therefore maintain the balance of the entire system. The wonder of nature's self-regulation is personified in these species.

Feel free to add any species you believe to be keystone to their ecosystems.

The Top Ten

Sea Otters

These guys clearly love to play in their spare time. It's kinda funny to watch them play. So is that their keystone contribution, comedic relief? No, but most would agree that's a nice aside.
Sea otters prey on sea urchins. In turn, sea urchins feed on kelp forests. Left unchecked, sea urchins can decimate kelp forests, and this has a negative impact on many creatures that rely on the kelp for survival. The whole ecosystem suffers or fails. Thanks, sea otters.
Beavers

The beaver is a primarily nocturnal, large, semiaquatic rodent. The genus Castor includes two extant species: the North American beaver (Castor canadensis) and the Eurasian beaver (Castor fiber). Beavers are known for building dams, canals, and lodges, significantly shaping their ecosystems and creating... read more

Beavers are ecosystem engineers, and their dam building provides still water, which allows a host of other species to flourish.
Wolves

The wolf (Canis lupus), also known as the gray or grey wolf, is a large canine native to Eurasia and North America. Over 30 subspecies of Canis lupus are currently recognized. Gray wolves represent the wild subspecies. As the largest extant member of the Canidae family, the wolf is distinguishable from... read more

Wired to take out the weak, sick, young, and elderly, it's commonly known that these predators actually help ensure the overall health of their prey species. Apex predators tend to keep the balance in their ecosystems through this behavior.
Now, it's true this branch of predators is the bane of farmers of livestock in their ecosystem, as they do indeed take the easy meal sometimes provided by this interaction. To that point, I would simply say that it is us who have encroached on their ecosystem, and not the other way around.

They are also responsible for regulating deer populations. When deer are overpopulated, they tend to destroy natural fauna, preventing birds and other animals from living in it. This is why predators such as wolves are considered significant animals in the keystone species category.
African Elephants

African elephants are elephants of the genus Loxodonta. The genus consists of two extant species: the African bush elephant, Loxodonta africana, and the smaller African forest elephant, Loxodonta cyclotis. They are the largest land animals on Earth and are native to various habitats across Africa.

On the savannahs of Africa, these magnificent creatures graze on small trees. This allows sunlight to reach the grass below. The grasslands flourish and provide an essential food source for a myriad of animals and, in turn, provide cover for predators stalking these herds. Without the elephants (and other tree leaf munchers), the savannah would become a forest or scrublands.
Jaguars

The jaguar (Panthera onca) is a large cat species and the only living member of the genus Panthera that is native to the Americas. It is the largest cat in the Americas and the third largest cat species in the world, behind only tigers and lions.... read more

Another apex predator. In the rainforests of Central and South America, they prey on a wide variety of species (87) and keep those prey animal numbers in check.
American Alligators

The American Alligator digs burrows in the sand that provide them with warmth. When they leave, the burrow provides many species with a new home. The alligators are also an apex predator and keep prey animal numbers in check.
Hummingbirds

Hummingbirds are birds from the Americas that constitute the family Trochilidae. They are among the smallest of birds, with most species measuring between 7.5 and 13 cm in length. Known for their rapid wing beats and ability to hover, they play a crucial role in pollination across many ecosystems.

Pollinators.
Starfish

Starfish, or sea stars, are star-shaped echinoderms belonging to the class Asteroidea. Common usage frequently includes ophiuroids under this name, although they are more accurately called brittle stars or "basket stars." Starfish are noted for their radial symmetry, diverse species, and ability to regenerate... read more

Starfish eat mussels, which have no other natural predators. Without the starfish, the mussels would overwhelm their particular ecosystem, and many other species would suffer or die off.
In areas where boating in freshwater lakes is popular, it's important that boaters check their watercraft for these mussels before and after each launch. The mussels attach and spread to other bodies of water. The result is devastating, as there are no starfish to prey on the mussels. Mussels are often an invasive species.
Bees

Bees are flying insects in the order Hymenoptera that are essential for pollinating flowering plants. They play a vital role in agriculture and natural ecosystems by facilitating plant reproduction. Bees also produce honey and beeswax, and some species live in complex social colonies.

Pollinators. The plants flourish and provide shelter and food for insects, and they, in turn, become food for other creatures, including birds.
The bee/plant relationship is also highly symbiotic, mutually assured existence.

The bee population is sadly in decline, mostly due to all the chemicals we humans use in our fields.
Killer Whales

The Orca, or Killer Whale (Orcinus orca), is a toothed whale belonging to the oceanic dolphin family, and is its largest member. Recognizable by its distinctive black-and-white coloring, the Orca is a cosmopolitan species found in all oceans, from polar to tropical regions.... read more

Yes, as apex predators, these guys provide balance to the population of prey species within their ecosystems. Thanks for adding.

Beautiful and intelligent creatures. Consider yourself lucky if you spot one while kayaking!

The Newcomers

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Dragonflies

Dragonflies are amazing and beneficial insects, as they eat mosquitoes, flies, and many other types of bothersome insects. They generally do not live long as adults, but can eat anywhere from 30 to 100 mosquitoes per day. They are tremendous and relentless hunters. Once they lock in on their tiny intended prey, it's over.
Dragonflies can see in 360° and can fly at speeds of up to 35 mph.
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Arctic Fox

The Arctic fox (Vulpes lagopus), also called the white fox, polar fox, or snow fox, is a small fox native to the Arctic regions of the Northern Hemisphere. It is commonly found throughout the Arctic tundra biome. This animal is well adapted to cold environments, with thick, warm fur that also serves... read more

The Contenders

Gopher Tortoises

This tortoise digs large burrows, which provide shelter for over 350 species.
Thanks, bud.
Eagles

Eagle is the common name for many large birds of prey in the family Accipitridae. Eagles belong to several genera, some of which are closely related. Most of the 60 species of eagle are found in Eurasia and Africa. Outside of these regions, only 14 species exist, with 2 in North America, 9 in Central... read more

Thanks for adding.
Pacific Salmon

The salmon die after spawning and provide a feast for many other creatures, including bears and eagles.
Earthworms
Aardwolves
Tiger Sharks

The tiger shark is a species of requiem shark and the only living member of the genus Galeocerdo. It is a large macropredator that can grow to over 5 meters in length. Tiger sharks are commonly found in tropical and temperate waters, particularly around central Pacific islands.

They'll eat almost anything, including sea turtles and dugongs in the Western Australian seagrass beds. Take them out of that ecosystem and the seagrass gets overgrazed. Fish lay their eggs in the seagrass. More sea turtles and dugongs mean fewer fish and less prey for other species.
Cheetahs

The cheetah (Acinonyx jubatus) is a large cat native to Africa and central Iran. It is the fastest land animal, capable of reaching speeds between 80 and 128 km/h (50 to 80 mph), with the fastest reliably recorded speeds being 93 and 98 km/h (58 and 61 mph). The cheetah has adaptations for speed, including... read more
Amazon River Dolphins
Prairie Dogs

Despite the name, prairie dogs are not canines. They are herbivorous burrowing rodents belonging to the genus Cynomys and are native to the grasslands of North America. Prairie dogs are actually a type of ground squirrel... read more
Cougars

The cougar, also known as the mountain lion, puma, panther, or catamount, is a large felid of the subfamily Felinae native to the Americas. It is the second-heaviest cat in the Western Hemisphere, after the jaguar. Cougars have one of the largest ranges of any wild terrestrial mammal, extending from... read more
Anacondas

Anacondas are a group of large snakes of the genus Eunectes. They are found in tropical South America and are known for their size and aquatic habitat. The green anaconda (Eunectes murinus) is the heaviest and one of the longest snakes in the world.... read more
Asian Elephants

Native to the forests and grasslands of South and Southeast Asia, the Asian elephant is one of the largest land mammals. Unlike their African counterparts, they have smaller ears, and in most populations only the males have prominent tusks. Asian elephants are highly social animals and typically live... read more
Chinese Alligators
Corals
Moose