The simaruba clade of Bursera • El clado simaruba de Bursera

Bursera  is a Mexican group par excellence. Of the nearly 100 species in the genus, more than eighty are found in Mexico. Incredibly, more than half of these species are from just three Mexican states: Michoacán, Guerrero, and Oaxaca. In some places, as many as eight or ten species can be found in a single general area. Because of their  abundance, incredible species diversity, and often spectacular shapes and colors, these trees are unmistakeable members of the tropical dry forests of Mexico. The simaruba clade of Bursera is remarkable for its incredible ecological breadth and the diversity in shapes and sizes of its members, which can be found from rainforest to very dry tropical deciduous forest. In Colombia, there is a species that is a giant rainforest tree, and in Central American there is a species that grows as a rainforest epiphyte! Below are images of the Mexican species, arranged more or less in order from driest to wettest. Our work with this group involves detailed measurements of the trunk dimensions, which is why many of the photos show us up in the trees.

Bursera longipesBursera longipes This beautiful tree is found in the central Balsas Depression in central southern Mexico. It grows in very dry forest with many other Bursera species and many columnar cacti. The middle photo from atop a B. longipes while taking measurements of the branches, and shows the columnar cactus Neobuxbaumia and two other Bursera species. The photo right of center is of a tropical dry forest in which B. longipes is one of the most common trees. You can see the red to copper bark and bluish foliage here and there across the hillside. The largest individual we have seen, at lower right, is in the parking lot at the Xochicalco archeological site in Morelos state. 
 Bursera longipes
Bursera longipes   Bursera longipes woods   Bursera longipes Xochicalco

Bursera grandifolia

Bursera grandifolia leaves
With large, arcing trunks that branch near the base, this species looks like an enormous rounded shrub. Bursera grandifolia does indeed have very large leaflets, which tend to be very fuzzy. The species is found in tropical dry forests of central Mexico. The greenish gray inner bark contrasts strongly with the reddish outermost bark, making this species a striking member of the dry forest flora. 
Bursera grandifolia     
Bursera grandifolia female flowers
The flowers of Bursera species are usually produced in male and female versions, though there are often exceptions. This photo shows the female flowers of B. grandifolia, which have three petals.
Bursera grandifolia male flowers
The male flowers, in contrast, have five petals.

Bursera instabilis

This strange species from western Mexico begins life like a normal tree, with a conventional trunk and branches that all support their own weight (left). With age, the branches begin to grow back on themselves, growing around and around within the crown of the tree. These branches rest on earlier-formed, self-supporting branches, much in the way that a liana would. One such branch removed from the tree is shown at right. It was 8 cm in diameter and 4 meters long! 
Bursera instabilis joven   Bursera instabilis canopy     Mark in B. instabilis crown     Lianescent branch of Bursera instabilis
Bursera instabilis with Tillandsia
Bursera instabilis Jalisco

Bursera arborea

This species is remarkable in the simaruba clade for being the species with the thinnest twigs. Whereas all of the other species have very thick twigs, the young shoots of B. arborea are remarkably slender. The species is found in tropical dry forest on the Pacific coast of Mexico. These photos were taken in Jalisco state. 
Crown of Bursera arborea Bursera arborea     Trunk of Bursera arborea

Bursera cinerea

This species grows on the fringes of lowland dry tropical areas, at the transition to moister highland  vegetation in Oaxaca and Veracruz. These magnificent trees are particularly striking for the deep red color of their trunks, which are an amazing sight sprawling in deep, shady canyons, as at left, or ascending in open forest, as at right. 

  red trunk of Bursera cinerea     Julieta and Bursera cinerea     Bursera cinerea

Bursera roseana

Another large, B. simaruba-like tree, this species was formerly known as Terebinthus acuminatus. Like some other members of the simaruba clade, this species grows in moist canyons in the transition zone between highland pine-oak forest and lowland tropical subdeciduous forest. It is very hard to tell apart from B. simaruba and B. attenuata
Bursera acuminata habit   Trunk of Bursera acuminata    Mark climging Bursera acuminata

Bursera attenuata

This species is similar in many respects to B. simaruba, differing in some leaf characteristics. It grows in fairly tall, moist tropical subdeciduous forests of the Pacific coast of Mexico. In some places, it occurs very close to sharp transition zones, with pines and oaks growing just above a zone of broadleaf forest. 
Trunk of Bursera acuminata
 Bursera attenuata    Mark in Bursera attenuata

Bursera simaruba

This is the most widespread species of Bursera, occurring from southern Florida and the Caribbean, along both coasts of Mexico to South America. The species is highly variable and is found in everything from tropical dry forest to tall rainforest. The images in the upper row are from rainforest on the Gulf coast of Mexico.
Bursera simaruba in the rainforest   Red trunks of Bursera simaruba     Bursera simaruba seedling   
Bursera simaruba Tabasco
Bursera simaruba as a landscape plant in the Comalcalco archaeological site in Tabasco.
salt-pruned Bursera simaruba Bursera simaruba pruned and shaped by salt laden sea breezes just above the beach in Veracruz.
Bursera simaruba living fence Bursera simaruba is often used as a living fence. Thick sections of branch readily root and make perfect fence posts that don't rot in tropical climates as dead wooden posts would. This fence is very close to the Gulf in Veracruz.
Bursera simaruba Chamela
Bursera simaruba is also found on the Pacific slope, from Sonora to South America. This photo is from a shady arroyo in the Chamela research station on the coast of Jalisco. The photos in the row below are also from the coast of Jalisco and Nayarit, where B. simaruba often grows in tall shady forests with Orbigyna palms endemic to the central Mexican Pacific.
Bursera simaruba Jalisco
Bursera simaruba Jalisco   Burera simaruba Nayarit
Bursera simaruba Cahuita Costa Rica    Bursera simaruba Palo Verde    Bursera simaruba Palo Verde
In Mexico, the Pacific and Atlantic populations of Bursera simaruba are widely separated. Where the land narrows in Central America, these plants can be found on both coasts very close to one another in very different forest types, from Caribbean slope rainforest to Pacific dry forest, as in these images are from Costa Rica. At left are trees from the Caribbean, at Cahuita, and at the Palo Verde research station on the Pacific in the two remaining images.

Bursera simaruba with MIcrocycas calocoma
Bursera simaruba is found on all the islands of the Caribbean, from the smallest to the largest. Here, we show it growing with the cycad Microcycas calocoma in dense woods on limestone.
Bursera simaruba Pinar del Rio
Bursera simaruba with Microcycas calocoma    Bursera simaruba with Microcycas calocoma    Bursera simaruba Pinar woods

Bursera laurihuertae

Our research shows that this enigmatic species is a member of the simaruba complex. It is endemic to the low, dense tropical dry forests of the southern Isthmus of Tehuantepec and is very distinctive for its rounded, leathery leaves that have just three or even only one leaflet. 
Bursera laurihuertae
Bursera laurihuertae and Julieta    Bursera laurihuertae trunk   Bursera laurihuertae bark

Bursera ovalifolia

This species was only recently recognized as an entitiy distinct from Bursera simaruba. It grows in warm, rather moist tropical deciduous forests on the Pacific coast of Mexico. It is sometimes hard to tell from B. simaruba but has longer petiolules and much smaller fruits. The three photos on the left in the row below are from Guerrero; the one on the right is from the central dry depression of Chiapas.
Bursera ovalifolia
Bursera ovalifolia leaves   Bursera ovalifolia roots    Bursera ovalifolia Chiapas
 Bursera "longicuspis" (ovalifolia)
We visited the type locality of Bursera longicuspis in Chiapas, to find that the plants there are individuals of B. ovalifolia growing at the upper elevational extent of the species, in the transition to oak forest. The plants seemed shorter and squatter than those at lower elevations.
Bursera ovalifolia
Bursera species usually flower and start to leaf out just as the dry season is ending. This Bursera ovalifolia in the forest of the Chamela resarch station in Jalisco is crowned with leaves in the first week of rain of the season. The rest of the trees in the forest are not far behind.

Bursera krusei

This species is very distinctive for its leaves with three large hairy leaflets. It grows in dry tropical forest in Guerrero and Oaxaca.
Bursera krusei habit
Bursera kruseis on a cliff   Bursera krusei leaves and branches

Bursera standleyana
Tree with Bursera standleyana

This remarkable species is a hemiepiphyte. That is, it grows high in other trees, but sends long, flexible, liana-like roots down to the forest floor. It is known only from the moist forest of the central and southern Pacific slopes of Costa Rica. In the photo with arrows, the upper arrow indicates one of the arching branches of B. standleyana and the lower one highlights the supporting tree. The leaves of B. standleyana can have five, three, or even just one leaflet.
Bursera standleyana
Bursera standleyana branches   Bursera standleyana roots and stems   Bursera standleyana roots and canyon
 Julieta with B. standleyana leaves Leaves of Bursera standleyana silhouetted   Bursera standleyana trifoliolate leaves   Bursera standleyana uni and penta foliolate leaves

Bursera shaferi

Bursera shaferi     Bursera shaferi habitat     Bursera shaferi leaves
The group of Bursera species that are endemic to the islands of the Caribbean appears to be part of the simaruba clade. Bursera shaferi is a little-known small tree that only grows on limestone mountains in Pinar del Río. 

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all material © 2002 Mark E Olson