I was on sabbatical the 2017-2018 academic year, seems like years ago. We spent the fall semester in Missoula, Montana and the spring in
Oaxaca, Mexico, our odyssey ended back in Ithaca. Blog posts from that era, highlighting monarchs and milkweed are here from the west and Mexico. But, one post I never got to until now was perhaps the most astonishing, that of our adventures on the hunt for monarchs and milkweeds in Madagascar. That month between Oaxaca and returning to Ithaca. This follows up on observations that are laying the foundation for my next research and writing projects, continuing on from my recent book . Here we go. Monarchs and Milkweeds
It starts here, near our departure from Oaxaca, Mexico, what a a place! Here I am standing next to a city “tree” in Oaxaca, a fabulous specimen of Pachypodium lamerei, a stem succulent member of the milkweed family (Apocynaceae), native to Madagascar.
Staring in Mexico, we traveled to Madagascar via a few days in Europe. Some of the M&M European adventures were highlighted here.
Travelling in Madagascar wasn’t always easy, but it was usually amusing!
Madagascar is one the largest islands on the planet, having three times the land area of England and about half the population of the same (30 million people). Human population density is not high, but there is massive environmental destruction via deforestation, mining, and forms of natural resource extraction. It’s one of the poorest countries in the world, but also one of the richest in terms of biological diversity. The only place where lemurs live (there were 111 species)… but endemism overall is remarkable…. Of the >10,000 plants species and nearly 1,000 vertebrate animal species, >85% of each group only occur on Madagascar. Madagascar is the only home for 6 of the world’s 8 baobab species, 1000 of the world’s orchids, and an entire family of spiny plants Didiereaceae.
Rice is the major crop of Madagascar, transplanted from Indonesia some 2000 years ago.
Despite being only 400 km from Africa (across the Mozambique channel) Madagascar was not colonized by humans until about 2000 years ago. That’s probably kept these biological riches intact for so long. Extinction is now rampant and rapid in Madagascar, with the two most prominent losses being Elephant birds (part of the extinct family Aepyornithidae) and some 15 species of giant lemurs, all of which went extinct since human colonization.
But I was most interested in seeing the Apocynaceae of Madagascar, especially a selection of the stem succulent Pachypodiums (21 species in total, with 16 from the the island). Here is P. brevicaule a low “shrub”, flowering in a outdoor hotel garden. We didn’t make it to the well-known population on Mt. Ibity.
In addition, we did find Calotropis procera, a close relative of our N American milkweeds, but of old world origin. I previously wrote about how our common milkweed Asclepias syriaca got its “wrong” name because somebody confused it with this plant ( Calotropis).
Calotropis procera is host to several butterflies in the Danainae, the subfamily that includes monarchs
One of our stops was in Isalo National Park, where we found P. rosulatum subspecies gracillus.
Hiking in Isalo National Park
Still hiking in Isalo National Park
A famed specimen of the fat plant P. rosulatum gracillus at Isalo. Pachypodiums are all deciduous perennials.
In another hotel garden is P. rutenbergianum, a small tree like Pachypodium. They don’t have wood per se, but are stem succulent
Spines of P. rutenbergianum. Recall that sharp protrusions on plants come in at least 3 forms: spines (which are evolutionarily modified leaves), thorns (modified stems), and prickles (epidermal protrusions).
Bird nest in P. rutenbergianum
Back on the road, more rice!
Gomphocarpus fruticosus is native to mainland Africa and weedy in Madagascar. The African Queen butterfly, Danaus chrysippus, a close relative to our North American Monarchs and Queens. What I began to see all throughout Madagascar was a recapitulation of the flora and fauna I knew from North America, but with alternate species. Gomphocarpus is a genus of 250 or species that is the African milkweed radiation.
A familiar friend, the oleander aphid, Aphis nerii, on 6 continents.
An unidentified Lygaeid bug… wherever I see Apocynaceae all over the world, I find these seed bugs. Great research on their adaptations being done by Georg Petschenka.
Seeds of Gomphocarpus fruticosus
And the African Queen butterfly, Danaus chrysippus
Up close, a flea beetle on the same plant. We don’t have many (known) specialized flea beetles of the Apocynaceae, but my colleague Susanne Dobler is obsessed with them.
A genus that I love, mostly stem, the vining Cynanchums. Here is C. perreri, thanks to Prof. Dr. Sigrid Liede-Schumann, of the University of Bayreuth for the ID.
Cynanchum perreri from Andringitra National Park
And the obligatory African queen on Cynanchum perreri (Andringitra National Park)
A fabulous find on a 15 mile mountainous hike in Andringitra National Park, the little known Cynanchum appendiculatum (Choux), again thanks to Prof. Dr. Sigrid Liede-Schumann, of the University of Bayreuth for the ID.
And where the Cynanchums are, so too are the Lygaeid bugs
At the end of the hike in Andringitra, more Gomphocarpus fruticosus. But with a very special visitor…
In north America there are no Milkweed-specialized grasshoppers, but here is the Madagascar Milkweed Rainbow Locust, Phymateus saxosus. Note the awesome aposematic coloration, which advertises the toxicity this hopper gains from the milkweed’s cardiac glycosides. This was discovered at about the same time as sequestration in monarchs was found, in the late 1960s. More on this history and convergent evolution in my book Monarchs and Milkweed. Also note the mass of little cocoons. These were likely Cotesia parasitoids that emerged from a parasitized African queen caterpillar!
Madagascar Milkweed Rainbow Locust, Phymateus saxosus (immature stage, or nymph, note that wings are not fully developed). Again note the mass of little cocoons. These were likely Cotesia parasitoids that emerged from a parasitized African queen caterpillar!
Madagascar Milkweed Rainbow Locust, Phymateus saxosus (immature stage, or nymph, note that wings are not developed)
An adult of the Madagascar Milkweed Rainbow Locust, Phymateus saxosus
An adult of the Madagascar Milkweed Rainbow Locust, Phymateus saxosus
In another part of Andringitra, here is Pachypodium densiflorum
The landscape of Pachypodium densiflorum
The awesome tomato-like flower of Pachypodium densiflorum
Recruitment of young Pachypodium densiflorum
Pachypodium densiflorum growing among what I believe is Kalanchoe tomentosa.
Pachypodiums come in many shapes and forms, here is tree-form P. geayi
Pachypodium geayii, no wood, think of it like a hard spongy cactus like tree milkweed.
A dreamy grove of Pachypodium geayii in Tsimanampetsotsa National Park (also home to many baobobs)!
Side stop to look for Pachypodium horombense
Found, but I wasn’t sure we had the right species ( Pachypodium horombense) until I saw the flower
The Madagascar palm, perhaps the most widely cultivated species, Pachypodium lamerei here in the wild
Pachypodium lamerei. The spines on Pachypodiums are modified leaf buds, and thus when leaves drop, new leaves cannot push out from the dormant buds (that is what the spines have become)… this contributes to the palm-like look of Pachypodiums, keeping leaves only on the top (in part, also, because the Pachypodiums are deciduous.
Spines of Pachypodium lamerei
North of Tulear we hit the beach, got sand fleas embedded in our feet, and searched for Pachypodium mikea.
Pachypodium mikea is a newly described species, closely related to P. geayii.
Bird nest in Pachypodium mikea
What a long beautiful trip it has been. So lucky to look for monarchs, milkweeds, Pachypodiums, and their bugs in Madagascar. If you want to read more about the convergence of plant and insect communities in N America and African milkweeds, please do check out my book . Also a great gift for naturalists, butterfly enthusiasts, and plant lovers. Monarchs and Milkweeds
You write, “Gomphocarpus is a genus of 250 or species that is the African milkweed radiation.” This use of the word “radiation” perplexes me. Is this a technical term in ecology?
Right, yes, a a technical term in evolution, I suppose 😉 Here is how I imagine the process of radiation… There was a common ancestor (single species) of all milkweeds that existed in Africa. On that continent, it was happily evolving. Perhaps 20 million years ago, an event (who knows what!) led to a small number of these plants arriving to the Americas. Then, these two sets of plants (again, probably one species) started independently evolving because they were on these two highly separated continents. Adaptive radiation is the process by which new species are formed and multiply. In the Americas, that radiation (over some 5-20 million years) led to the formation of about 140 species in the genus we call Asclepias…. all decedents of the original colonist from Africa. Over a similar period, the same ancestor in Africa gave rise to the 250 species we call Gomphocarpus. The two groups share an ancestor from before the Americas were colonized… but then evolution independently generated a set of species on the two continents, each one being a “radiation”. Remarkably there are many species of Asclepias and Gomphocarpus that look similar, presumably because there was similar “potential” buried in the genome of the common ancestor. Sorry for all the jargon folks!! Nonetheless, adaptive radiation is a really important process in evolutionary biology, and one that is hard for any of us to truly imagine.
You said, “Gomphocarpus is a genus of 250 or species that is the African milkweed radiation.” But when I made a search for a listing of these 250 species or more I find that there are only roughly 184-187 and of those only 22 are actually accepted as being of that genus. So, my question is where is it that you got the numbers for 250 or more species of Gomphocarpus?
Wonderful and educational adventure, Thank you for sharing, Love it!!!
This must have been stunning—exploring the pristine nature of Madagascar. Cool insect pics! Thanks for sharing!
Thank you! Unfortunately, there is little that is pristine in Madagascar, or anywhere in the world really. Nonetheless, I feel very fortunate to have gone there and explored some of these amazing creatures. All my best!