Phytomyza glabricola

Kulp, 1968

inkberry holly leafminer

Phytomyza glabricola is a leaf-mining in the , to the eastern United States. The exhibits -associated divergence on two holly species, Ilex glabra and I. coriacea, with on each host showing substantial genetic divergence and reproductive isolation. Development time differs dramatically between host races: 2-4 weeks with multiple per year on I. glabra versus 9-10 months with a single generation per year on I. coriacea. Despite these differences, from both hosts emerge synchronously in mid-January to mid-February. The species provides a well-documented case of ecological speciation via host shift.

Pronunciation

How to pronounce Phytomyza glabricola: /ˌfaɪtoʊˈmaɪzə ˌɡlæbrɪˈkoʊlə/

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Identification

are small resembling houseflies; no morphological differences exist between adults from different plants in external characters or . are tiny found within serpentine leaf mines. The presence of snakelike galleries (leaf mines) on holly leaves is diagnostic for larval activity. Mines end with a small exit hole cut by the larva before . Leaves with numerous adult feeding punctures often show curled or puckered margins.

Habitat

Coastal plains of the eastern United States; leaf mines within leaves of holly plants. Found in and syntopic stands of Ilex glabra and I. coriacea, often in mixed stands of both holly .

Distribution

Eastern United States from New York to Florida. Range spans that of Ilex glabra (Maine to southern Florida and west to northeastern Texas) and I. coriacea (North Carolina to northern Florida to Texas). Documented from New York, New Jersey, Delaware, Maryland, Virginia, North Carolina, South Carolina, Georgia, and Florida.

Seasonality

emerge synchronously from both plants in mid-January to mid-February. feed through winter and early spring on warm days; occurs in spring. is precisely timed to coincide with appearance of tender new holly leaves.

Diet

; feed internally within leaf mines on of holly leaves. females feed on sap exuded from feeding punctures made with their .

Host Associations

Ilex glabra - primary Original ; with 2-4 week development time
Ilex coriacea - novel -shift ; with 9-10 month development time
Ilex vomitoria - associated Additional association reported in some studies

Life Cycle

Development time varies dramatically by : 2-4 weeks with multiple per year on Ilex glabra; 9-10 months with single generation per year on I. coriacea. In greenhouse conditions, both host races develop in approximately 43-52 days. form serpentine leaf mines, feeding between upper and lower leaf surfaces. Before , larvae cut a small window in the leaf surface to enable escape. Adults emerge in mid-January to mid-February regardless of host plant.

Behavior

Female uses sharp to pierce leaf surface for both -laying and feeding; feeding punctures exude sap droplets consumed by the . -associated phenological differences exist despite synchronous adult . Females will oviposit on non-natal host plants, but offspring survival is restricted to intra-host matings.

Ecological Role

Leaf-mining on holly ; part of a radiation of 14 closely related Phytomyza species on Ilex . Represents a documented case of host race formation and potential incipient speciation via ecological specialization. Host plants may drop heavily infested leaves prematurely as a defense, killing undeveloped .

Human Relevance

Minor ornamental pest on holly ; leaf mines and feeding punctures reduce aesthetic value of foliage. Sometimes brought indoors on cut holly branches during winter holidays; will not emerge in homes.

Similar Taxa

Phytomyza ilicicolaAlso a holly on holly (Ilex opaca); distinguished by association and geographic range. P. glabricola specifically associated with I. glabra and I. coriacea rather than I. opaca.
Other Phytomyza species on Ilex14 closely related form a radiation on Ilex ; P. glabricola distinguished by specific host associations with I. glabra and I. coriacea and documented host race divergence.