Gekko monarchus is one of two species of Gekko known to occur in the Philippines with a distribution extending across a broader region in Southeast Asia. The other species is the widespread, invasive gecko, Gekko gecko. This distribution outside the Philippines differentiates this species from the ten currently recognized, endemic species of Gekko in the Philippines. Historically, Gekko monarchus was recognized to occur more broadly in the Philippines (Brown and Alcala, 1978); however, recent studies indicate that this species only occurs on the island of Palawan in the western Philippines (Brown et al., 2008, 2009; Linkem et al., 2010). Future investigations focused on this species may reveal that Gekko monarchus represents a complex of morphologically similar, but unique, species. Gekko monarchus is currently recognized to occur throughout Southern Thailand (Narathiwar, Phang Nga), Malaysia, Pulau Tioman, Johor, the Philippines (Palawan and possibly the Calamian Islands), Singapore, Kei islands, Indonesia (Borneo, Sumatra, Java, Sulawesi, Nias, Ambon, Ceram, Irian Jaya), and Papua New Guinea. 

Recent studies and increased survey efforts throughout the Philippines have resulted in a dramatic increase in the diversity of gekkonid lizards in the country. The archipelago is now known to support ten genera and at least 48 described species in the genera Cyrtodactylus (9 species), Gekko (12–13), Gehyra (1), Hemidactylus (5; including platyurus, a species formerly assigned to Cosymbotus), Hemiphyllodactylus (2), Lepidodactylus (6), Luperosaurus (8), Pseudogekko (4), and Ptychozoon (1) (Taylor, 1922a,b; Brown and Alcala, 1978; Brown and Diesmos, 2000; Brown et al., 1997, 1999, 2007, 2008, 2009, in press; Gaulke et al., 2007; Linkem et al., 2010; Welton et al., 2009, 2010a, b; Zug, 2010).

 

Ten species of Gekko are considered endemic to the archipelago (Brown et al., 2009; Linkem et al., 2010) and two additional species with broad geographic distributions (G. gecko, G. monarchus) are also known from the country (Taylor, 1922a, b; Brown and Alcala, 1978; Ota et al., 1989). The ten endemic Philippine species are G. athymus, G. carusadensis, G. crombota, G. ernstkelleri, G. gigante, G. mindorensis, G. palawanensis, G. porosus, G. romblon, and G. rossi. These species represent a considerable range in body size, general appearance, and ecological attributes, but all possess the following combination of morphological traits: (1) body size moderate, with relatively long, slender limbs; (2) near complete absence of interdigital webbing or cutaneous body expansions; (3) dorsal tubercles arranged in longitudinal rows on the dorsum (except for G. athymus, in which dorsal tuberculation is absent); (4) scales of dorsum between tubercle rows minute, non-imbricate; (5) scales of venter enlarged, imbricate, flat; (6) differentiated postmentals elongate; and (7) subcaudals enlarged, plate-like (Brown and Alcala, 1978; Brown et al., 2007, 2008, 2009).

Gekko monarchus can be distinguished from congeners by the following combination of characters (1) medium body size (SVL 56.2–80.7 mm for adult males; 40.6–69.7 for females); (2) vertebral coloration with dark transverse spot rows; (3) supralabials 11–13; (4) preanofemorals 31–40; (5) Toe IV scansors 13–15; (6) internasals contacting rostral 1 or 2; (7) scales contacting nostril 5; (8) midbody ventral scales 38–44; (9) midbody dorsal scales 96–112; (10) midbody tubercle rows 16–20; (11) vertebral tubercles in axilla–groin distance 18–23; (12) paravertebral scales in axilla–groin distance 171–203; (13) ventral scales in axilla–groin distance 57–61.

Amboine (= Ambon, Indonesia)

Gekko monarchus is currently recognized to occur throughout Southern Thailand (Narathiwar, Phang Nga), Malaysia, Pulau Tioman, Johor, the Philippines (Palawan and possibly the Calamian Islands), Singapore, Kei islands, Indonesia (Borneo, Sumatra, Java, Sulawesi, Nias, Ambon, Ceram, Irian Jaya), and Papua New Guinea.

Continent: Asia
Distribution: S Thailand (Narathiwar, Phang Nga), Malaysian peninsula, Pulau Tioman, Johor: Pulau Besar, Philippines (Palawan, Calamian Islands, Mindoro, Luzon), Singapore, Kei islands, West Malaysia, Indonesia (Borneo, Sumatra, Java, Sulawesi, Nias, Ambon, Ceram, Irian Jaya), Papua New Guinea  
Type locality: Amboine (= Ambon, Indonesia)

SVL 56.2–80.7 mm for adult males; 40.6–69.7 for females

Traditionally, Gekko monarchus has been confused with the morphologically similar species G. mindorensis. Both species often have banded morphologies, and scale and pore counts, as well as coloration and other diagnostic features are often needed to tell these species apart. They are not known to occur sympatrically, which aids in species identification in the wild.