The broader leaves suggest Turnera ulmifolia, although I can't find any other 'academic' sites which are usually reliable other than the link below, you can enlarge the drawing which shows broad leaves. There may be others!
http://edis.ifas.ufl.edu/fp593
Turnera diffusa var. aphrodisiaca ..
http://aggie-horticulture.tamu...
http://aggie-horticulture.tamu...
Turnera diffusa ...
Phillip Schappert, a biologist with the University of Texas at Austin, has photographed the plant growing in Starr County west of Roma, near where FM 650 meets US 83. Though he doesn't live in the Valley, he may be able to give you directions to the plants he photographed.
http://www.wildflower.org/expe...
http://www.sbs.utexas.edu/phil...
I found a document which describes Turnera ulmifolia :
Turnera ulmifolia L. is a polymorphic polyploid complex of perennial weeds commonly called ‘Yellow Alder’. This variety is a dense compact shrub that has dark green foliage and bright yellow flowers.
Link headed: Turnera ulmifolia - eIJPPR
https://www.google.co.uk/#q=Tu...
Photo on a pdf isn't much help ..
http://www.bulletinofinsectolo...
I found photos of a reliably identified Turnera ulmifolia, the leaves are more ovate than yours.
http://www.comfsm.fm/~dleeling...
I found someone's very thorough research on this, with answers from people in the know. You need to read the whole article, take note of "Panama’s Turnera"
http://ntsavanna.com/elm-leave...
No crown in its flower and linear, short bracteoles are all we need to know to say with confidence that it is Turnera ulmifolia
I would say the "crown in the flower" is the part sticking out the middle above the orange-coloured stamens/anthers. Yours does have this, so that should exclude Turnera ulmifolia.
