Saturday, February 15, 2014

Smut fungi

On my way to the 3rd street promenade, I happened upon a Kusamaki tree (Podocarpus macrophyllus) that had its leaves covered with a dark soot-like material.  The sooty debris is actually a multicelular fungus in the taxonomic class Ustilaginomycetes, better known as "smut" fungi.  This particular smut has a fantastic backstory; do you see the white-covered "dots" along the bottom of the leaves?  These are female mealybugs (Pseudococcidae), which are phloem-feeding scale insects.  Male Pseudococcids are very short-lived and sexually dimorphic (so they look more like tiny little wasps with a single pair of wings!).  Due to their all-liquid diet, female mealybugs excrete large amounts of fluid rich in carbohydrates called "honeydew", which then attracts a diverse assemblage of ant species.  In exchange for the honeydew services, the ants defend mealybugs from predatory insects, like parasitoid wasps.  However, when ants are absent, the untended mealybugs will continue to drip honeydew leaving a sweet glassy film that then elicits the growth of the smut fungi!  The smut is antagonistic, eventually precipitating harm to both the mealybugs and host plant.  Here's a great paper by Johnson et al. 2001, which details that these symbiotic ant-tending interactions are at least 20 million years old!

Thursday, January 16, 2014

Atmospheric chemistry

The image above is a ground- and satellite-level perspective of the first day of the Colby Fire.  Atmospheric particulates, from both anthropogenic and natural processes, are especially relevant for fire & drought adapted ecological landscapes like southern California.  From the satellite image you can see smoke plumes being carried by Santa Ana winds from the interior basin through mountain passes in a "downhill" fashion toward the Pacific ocean.  Biological systems actively interact with the atmosphere, and these interactions vary with respect to both the chemistry and the composition of gasses (e.g. volatile organic compounds), particulates (e.g. partial combustion), and emissions (natural & anthropogenic contributions).  In fact, many native plant species are singularly adapted to respond to atmospheric "cues" (e.g. to initiate seed-germination post-fire).  Here's a great paper on the impact of atmospheric deposition on plant chlorophyll content by Prajapati & Tripathi (2008).

Saturday, December 14, 2013

Homogenization of Mediterranean flora

The name ascribed to the sclerophyllous shrublands typical of the Mediterranean biome varies tremendously: "kwongan" and "mallee" in Australia, "chaparral" in California, "matorral" in Chile, "fynbos" in South Africa, and varies more so throughout the Mediterranean basin: "mato" in Portugal, "maquis" or "garrigue" in France, "macchia" in Italy, "phrygana" in Greece, and the list goes on!  Just like the local names; the forests, woodlands, and scrub associated with Mediterranean climate zones are incredibly diverse and endemic-rich.  Since this vegetation-type is broadly adapted to summer drought and winter rains, it's also easily transferable anthropogenically across vast geographic distances and floristic regions.  For example; at the Santa Barbara Mission (pictured above) you can observe: [front of lavanderia] the Aloe tree (Aloe barberae) native to South African fynbos, [front of Mission] the Peruvian peppertree (Schinus molle) native to South American matorral, [hills in back] the coastal sage scrub vegetation native to Californian coastal chaparral, and [frame right] the Gum tree (Eucalyptus spp.) native to Australian mallee.  Here's an interesting paper on the "Homogeocene" epoch by Putz 1998.

Saturday, November 30, 2013

Hoverfly Batesian mimicry

At first glance, the insect visiting this Chrysanthemum flower looks just like a honeybee - but on closer inspection you can see the insect has a lot of the characteristics you'd expect to see on a fly: a single pair of wings, short antenna, and sucking mouth parts.  This insect is in fact a hoverfly! Also known as a flower fly or a syrphid fly, this European species of hoverfly (Eristalis arbustorum) is incapable of stinging, but is definitely converging on the morphology (shape, color, etc.) of a honeybee.  This form of mimicry is also known as Batesian mimicry - when a non-toxic palatable species looks like a toxic non-palatable species.  What is even more amazing is that the hoverfly, honeybee, and Chrysanthemum are all exotic (or non-native) species here in the central valley of California!  Here's a cool paper by Pfenning et al. 2001.

Monday, October 21, 2013

Chicken of the woods

Believe it or not, this sulfur shelf (Laetiporus sulphureus) is an edible bracket fungus that is touted for tasting like chicken! While it's native to both North America & Europe, this beautiful specimen was growing on a Carob tree (Ceratonia siliqua) that is actually native to the Mediterranean & a common element in Santa Monica residential areas.  The sulfur shelf is a saprophyte (detritivore) and causes internal rot on the trees it infects.  What's fascinating is that it's also possible for the sulfur shelf to absorb some of the toxic properties of its host tree; which sometimes can lead to gastrointestinal problems for folks that eat the fungus growing on trees like eucalyptus & some conifers.  Here's a great paper by Turkoglu et al. 2007.

Monday, August 12, 2013

Acridid grasshopper color polymorphisms

This is the nymph of an Acridid grasshopper, a paurometabolous insect that derives its family name from the Greek term akris, meaning locust or swarming grasshopper (which are also members of the Acrididae!). The color variation in Acridid grasshoppers is just spectacular, as is the role of coloration in this group: thermal regulation, crypsis, aposematism, sexual dimorphisms, and even as a means to promote (negative) frequency-dependent selection - wherein rare phenotypes are missed by predators that prefer common prey phenotypes.  Here's a great review paper by Bond 2007.

Thursday, July 4, 2013

The foot of a common house gecko

     While it can be found throughout Mesoamerica, the common house gecko (Hemidactylus frenatus) is a actually a native of southeast Asia.  The story is that the population started from escaped pets.  Here in El Salvador, the house geckos do exceptionally well in urban areas & suburban parks (where homes & 24hr street lights are abundant) and they seldom venture deep into the few remaining large natural areas.  How a gecko's feet work is simply spectacular: β-keratin spatula-shaped bristles arranged in plate-like footpads (white above) allow attractive intermolecular van-der-Waals forces (i.e. non-covalent bonds!) to form between the footpad & a given surface.  Here's a great paper by Herrera et al. 2005.